Add import of programs from Google calendar

@anthonywebb, this is my code to import watering programs from Google calendar.

This was lightly tested on a Debian 'testing' PC, with production:false. The socket.setBroadcast() fails consistently: this was the cause of my calendar code not loading, because it stops the script before any Google's data is received. (I locally disabled the UDP broadcast, that temporary patch was _not_ committed to the branch.)

Pascal.