Put GRSP definitions in opcodes specification document

[david284]

The GRSP responses are directly related to the opcodes, whilst only indirectly related to the service specifications (by virtue of the fact the services define the opcodes they use, and hence indirectly the GRSP codes) - i.e. I believe they are opcode specific, not service specific
Hence the GRSP definitions should be moved into the opcode specification document (I believe they are currently defined in the MNS service)
Also, whilst implementing the GRSP response in the compliance test, there are some responses that I don't believe are defined anywhere, or are duplicated - these are...

//	INV_CMD
//	Invalid Command
//	Invalid parameter
//	invalid state
//	Invalid Command
//	No EV

For completeness, the definitions I have found are..

const GRSP = {
OK: 0,
CommandNotSupported: 1,
NotInLearnMode: 2,
NotInSetupMode: 3,
TooManyEvents: 4,
NoEvent: 5,
InvalidEventVariableIndex: 6,
InvalidEvent: 7,
InvalidParameterIndex: 9,
InvalidNodeVariableIndex: 10,
InvalidEventVariableValue: 11,
InvalidNodeVariableValue: 12,
InvalidService: 252,
InvalidDiagnosticCode: 253,
UnknownNVM: 254
}