Add basic Z-Wave product database entries for Leviton (Company)

Add basic Z-Wave product database support for Z-Wave Products from Leviton. 

To start, I'm only adding the following items:
   VRI06-1LZ (Dimmer), VRS15 (Switch) and the newly added DZS15-1LZ (Switch)

The DZS15-1LZ is a new Leviton Z-Wave switch that's sold at Home Depot, so it doesn't yet have an entry in Pepper.  For now, I've copied the entry for the VRS15 (since it's almost identical) and I will tweak up the entry once we know more about it.