JSON RPC API input integers should be supported also in decimal format

[canepat]

See RPCDaemon behavior that supports integers. Silkrpc response to web3_clientVersion request with "id": 1 is currently:

{
    "error": {
        "code": 100,
        "message": "[json.exception.type_error.302] type must be number, but is string"
    },
    "id": 0,
    "jsonrpc": "2.0"
}