Added human readable JSON output for Device

[lostfields]

Human readable device information, instead of displaying enum values it will output enum key when JSON serializing the objects. Device setters also supports enum key.

[lostfields]

Earlier, JSON.stringify(groups) outputted

[{
  "_id":8440,
  "_name":"My House",
  "_devices":[{"_guid":"***","_name":"***","_operate":1,"_operationMode":3,"_temperatureSet":21,"_fanSpeed":0,"_fanAutoMode":3,"_airSwingLR":2,"_airSwingUD":2,"_ecoMode":0,"_actualNanoe":0,"_ecoNavi":0,"_nanoe":1,"_iAuto":0,"_airDirection":0,"_ecoFunctionData":0,"_insideTemperature":0,"_outTemperature":0,"lastSettingMode":0}]
}]

and now

[{
  "id":8440,
  "name":"My House",
  "devices":[{"guid":"***","name":"***","operate":"On","operationMode":"Heat","temperatureSet":21,"fanSpeed":"Auto","fanAutoMode":"AirSwingLR","airSwingLR":"Mid","airSwingUD":"Mid","ecoMode":"Auto","ecoNavi":0,"nanoe":"Off","iAuto":0,"actualNanoe":0,"airDirection":0,"ecoFunctionData":0,"insideTemperature":0,"outTemperature":0}]
}]

That may be a breaking change, it depends. Although it's more correct to do it this way since the serialized value is the same as the class definition.

[lostfields]

I've made it backwards compatible now, it will output the same as before with no breaking changes. To get the new output you have to set ComfortCloudClient.outputMode = 'pretty'

What do you think @marc2016 ?