Add Service.Switch to set away / home feature for Nest Cam.

[outaTiME]

Hi guys,

im add a missing feature for set away / home on Nest Cam using Switch ... I hope you find it useful !!!

[outaTiME]

Probably this switch logic must be in base class NestDeviceAccessory for each Nest device, but i don't know if im doing the things in right way.

NestDeviceAccessory has addAwayCharacteristic method and is used by NestThermostatAccessory and NestCamAccessory but i don't understand what it does.
Probably addAwayCharacteristic must be use and boolean value instead of number.

I'll be waiting for your feedback, thanks !!!