Can not read RCP Json Difficulty
[Description of the issue]
RCP Client on IgnitionCoin for example, response an array on difficulty:
￼
{
    "blocks" : 292896,
    "currentblocksize" : 2109,
    "currentblocktx" : 2,
    "difficulty" : {
        "proof-of-work" : 19.43194771,
        "proof-of-stake" : 206944.73437500,
        "search-interval" : 16
    },
    "blockvalue" : 95000000,
    "netmhashps" : 463.66431365,
    "netstakeweight" : 37192768469813.56250000,
    "errors" : "",
    "pooledtx" : 2,
    "stakeweight" : {
        "minimum" : 0,
        "maximum" : 0,
        "combined" : 0
    },
    "testnet" : false
}

Maybe thats why Miningcore throw an error?

 Newtonsoft.Json.JsonReaderException: Error reading double. Unexpected token: StartObject. Path 'difficulty'.


### Steps to Reproduce
getmininginfo rcp command, response an array on difficulty parameter:

"difficulty" : {
"proof-of-work" : 19.43194771,
"proof-of-stake" : 206944.73437500,
"search-interval" : 16
},

### Expected behavior

Miningcore reads PoW difficulty correctly.

### Actual behavior

throw an error:
 Newtonsoft.Json.JsonReaderException: Error reading double. Unexpected token: StartObject. Path 'difficulty'.

### Reproduces how often
100%

### Version
Release 44.
Net Core 2.1 on Windows.
