Changes made to error handling
Added NfieldErrorCode to sdk
Merge branch 'master' of github.com:NIPOSoftware/Test

Conflicts:
	Library/Exceptions/NfieldBadRequestException.cs
	Library/Exceptions/NfieldConflictException.cs
	Library/Exceptions/NfieldHttpResponseException.cs
	Library/Exceptions/NfieldNotFoundException.cs