[ALOY-1303] $.removeListener() should be called by $.destroy()

The [current implementation](https://github.com/appcelerator/alloy/pull/671) of ALOY-1237 uses the new $.addListener() method for any event listeners set on proxy objects via the XML. This way the user can remove all or specific event listeners via $.removeListener(). It would be better if the template for $.destroy() would include a call to $.removeListener() so that the user only has to call $.destroy() to both clean up listeners to global collections as well as local proxies.