Add Z-Wave Product: Remotec ZXT-120 AC IR Remote

As a result of the new Z-Wave Thermostat command classes I've added the
Remotec ZXT-120 Air Conditioner IR controller to the product database.

Tested as fully working!

zwavedb: http://www.pepper1.net/zwavedb/device/364
Product URL: http://www.remotec.com.hk/zaspx/product_content.aspx?aboutno=36&subaboutno=45&main=f