Add ability to specify cuda-affinity, cuda-devices and cuda-launch options in config.json
For now it is impossible to specify `cuda-affinity`, `cuda-devices` and `cuda-launch` options in the `config.json`. They are ignored.

```js
{
  "algo": "cryptonight",
  "api": {
    "port": "65055",
    "access-token": null,
    "worker-id": null,
    "ipv6": false,
    "restricted": true
  },
  "background": false,
  "colors": true,
  "cuda-launch": "98x30",
  "cuda-bfactor": 8,
  "cuda-bsleep": 100,
  "donate-level": 5,
  "log-file": null,
  "pools": [
    {
      "url": "pool.graft.hashvault.pro:7777",
      "user": "xxx",
      "pass": "x",
      "rig_id": "null",
      "use_nicehash": false,
      "tls": false,
      "tls-fingerprint": null,
      "variant": null,
      "keepalive": true
    }
  ],
  "print-time": 60,
  "retries": 5,
  "retry-pause": 5,
  "threads": null,
  "user-agent": null,
  "syslog": false,
  "watch": false
}
```

Miner is launched as `./xmrig-nvidia`, without command line arguments.

After the launch `config.json` is updated (see below). Have a look at `threads` and `blocks` values in `threads` section that does not match with `cuda-launch`).

```js
{
    "algo": "cryptonight",
    "api": {
        "port": 65055,
        "access-token": null,
        "id": null,
        "worker-id": null,
        "ipv6": false,
        "restricted": true
    },
    "background": false,
    "colors": true,
    "cuda-bfactor": 8,
    "cuda-bsleep": 100,
    "donate-level": 5,
    "log-file": null,
    "pools": [
        {
            "url": "pool.graft.hashvault.pro:7777",
            "user": "xxx",
            "pass": "x",
            "rig-id": null,
            "nicehash": false,
            "keepalive": true,
            "variant": -1,
            "tls": false,
            "tls-fingerprint": null
        }
    ],
    "print-time": 60,
    "retries": 5,
    "retry-pause": 5,
    "threads": [
        {
            "index": 0,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        },
        {
            "index": 1,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        },
        {
            "index": 2,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        },
        {
            "index": 3,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        },
        {
            "index": 4,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        },
        {
            "index": 5,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        },
        {
            "index": 6,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        },
        {
            "index": 7,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        },
        {
            "index": 8,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        },
        {
            "index": 9,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        },
        {
            "index": 10,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        },
        {
            "index": 11,
            "threads": 32,
            "blocks": 30,
            "bfactor": 8,
            "bsleep": 100,
            "sync_mode": 3,
            "affine_to_cpu": false
        }
    ],
    "user-agent": null,
    "syslog": false,
    "watch": false
}
```

Miner log
```
 * ABOUT        XMRig-NVIDIA/2.8.4 gcc/5.4.0
 * LIBS         libuv/1.8.0 CUDA/9.20 OpenSSL/1.0.2g microhttpd/0.9.44
 * CPU          Intel(R) Celeron(R) CPU G3930 @ 2.90GHz x64 AES
 * GPU #0       PCI:0000:01:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * GPU #1       PCI:0000:04:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * GPU #2       PCI:0000:06:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * GPU #3       PCI:0000:08:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * GPU #4       PCI:0000:09:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * GPU #5       PCI:0000:0a:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * GPU #6       PCI:0000:0b:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * GPU #7       PCI:0000:0c:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * GPU #8       PCI:0000:0d:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * GPU #9       PCI:0000:0e:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * GPU #10      PCI:0000:0f:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * GPU #11      PCI:0000:10:00 GeForce GTX 1060 6GB @ 1847/4004 MHz 32x30 8x100 arch:61 SMX:10
 * ALGO         cryptonight, donate=5%
 * POOL #1      pool.graft.hashvault.pro:7777 variant auto
 * API BIND     0.0.0.0:65055
 * COMMANDS     hashrate, health, pause, resume
[2018-11-24 22:19:38] configuration saved to: "/hive/miners/xmrig-nvidia/2.8.4/config.json"
[2018-11-24 22:19:38] use pool pool.graft.hashvault.pro:7777  54.37.87.105
[2018-11-24 22:19:38] new job from pool.graft.hashvault.pro:7777 diff 200007 algo cn/2
```
