[Android] Add optional <application> attributes via Rakefile

Hi everyone, 

I couldn't find a way to pass all the ```<application>``` attributes from the ```Rakefile```(or any other way) to the ```AndroidManifest.xml```. Looks like the only settable ones are icon and 'application_class'(translated to name) right now.

This enables all the possibles ```<application>``` attributes to be set on the ```Rakefile``` and passed to the ```AndroidManifest.xml```. I've removed the 'debuggable' and 'label' from the list, as those are treated differently.

I've added more lines of code than I wanted, but couldn't find a better way.

Anyway, this is more a 'Did I miss something?' than a 'This needs to be merged' kind of PR.

thanks!