Feature - add generic command handling

[gandazgul]

My main change is line 575 of the smart app. It checks if the device supports the command being sent and calls it directly even when no action is specified in the capabilities map.

This allows virtual devices that implement commands with the same name as the capability state (e.g. temperature()) to just work.

For temperature and humidity I did add actions that call temperate or setTemperature depending on which is supported (I have seen both used).

This should help people who are using the virtual sensors from smartthings with this bridge. A better sensor device handler fully compatible with this bridge is available here: https://github.com/gandazgul/mqtt-smartthings-devices/blob/master/devicetypes/gandazgul/mqtt-temperature-sensor.src/mqtt-temperature-sensor.groovy