Feature request: Option for device enumeration based on OpenCL device order
Currently nanominer sorts the devices by PCI busID. 
Unfortunately the PCI BusID information is not available through the OpenCL API which, as a consequence, breaks proper integration on MultiPoolMiner based software (e.g. MultipoolMiner, Nemos Miner etc.).
Could you please add an option (e.g. --deviceOrder OpenCL) which will allow nanominer to sort the devices based on OpenCL device ID?

OpenCL device order in my case is:
```
GPU#00 GeForce GTX 1080 Ti
GPU#01 GeForce GTX 1060 6GB
GPU#02 Radeon RX 580 Series (Ellesmere)
GPU#03 AMD Radeon (TM) RX 560 (Baffin)
```

Nanominer now:
```
nanominer -d
2019-06-10 07:36:23: CUDA driver version is 10.2, runtime version is 10.0
Detected 4 devices:
GPU 0  PCI 01:00.0  11264 MB  GeForce GTX 1080 Ti
GPU 1  PCI 04:00.0  6144 MB  GeForce GTX 1060 6GB
GPU 2  PCI 05:00.0  2048 MB  AMD Radeon (TM) RX 560 (Baffin)
GPU 3  PCI 09:00.0  8192 MB  Radeon RX 580 Series (Ellesmere)
```

Preferred result:

```
nanominer --deviceOrder OpenCL -d
2019-06-10 07:36:23: CUDA driver version is 10.2, runtime version is 10.0
Detected 4 devices:
GPU 0  PCI 01:00.0  11264 MB  GeForce GTX 1080 Ti
GPU 1  PCI 04:00.0  6144 MB  GeForce GTX 1060 6GB
GPU 2  PCI 09:00.0  8192 MB  Radeon RX 580 Series (Ellesmere)
GPU 3  PCI 05:00.0  2048 MB  AMD Radeon (TM) RX 560 (Baffin)
```
