Fhem tx

Man muss in Github einstellen was die Basis für den Pull-Request ist...

FHEM module now supports:
    battery and version messages
    power switch status message
    power switch on/off/toggle/statusRequest
    adds web commands to power switch
    verify and stores aes key
    correct deviceId check

TODO:
    rename SHC -> SHC_BASE, SHC_TEMP -> SHC_DEVICE (other proposals welcome!)
    implement dimmer
    have a closer look at SHC_BASE driver and remove unused stuff copied from JeeLink