Add (2852-222) Insteon Leak Sensor, LeakSensor device type

[mattj103]

Adds functionality for Insteon leak sensor. Leak sensor has 3 subaddresses Dry (1), Wet (2), and HeartBeat (4). Wet and Dry are always opposite state so ignoring dry. Device.getCurrentLeakState() returns true if leak is detected. Updated readme to include new device type.