Adding support for fxos

I'm working on adding phonegap developer app to firefox OS. I have it working pretty well, I wrote a blog post about it [on hacks.mozilla with a screencast of it running](https://hacks.mozilla.org/2014/09/phonegap-developer-app-preview-for-firefox-os/). I had to do a bunch of small fixes to the platform and to plugins for things to run smoothly. All fixes either shipped as part of cordova 3.6.3 or will ship with next plugins release soon.

I had to use a mix of cordova and phonegap tools to get it all working. I don't think this PR is ready to merge until PhoneGap gets all 3.6 goodies, but would truly appreciate any feedback.