Implemented support for metadata GENERIC type

I've tested this in a fork I've built to work with an older Cordova version (2.7.0) but everything should check out. 

Notes:
* Not actually compiled because I don't have a full Eclipse project of this
* I may (read: probably) have forgotten an import statement in Chromecast.java and ChromecastSession.java
* Only supports MediaMetadata of type GENERIC at the moment.
* Has a fallback to MEDIA_TYPE_MOVIE when anything fails (like metadata being null)