Fixed and Flexible layouts for Android.

This review adds the same functionality as exists on iOS for sprite builder's fixed and flexible layouts on android platform.

Note: I'm not happy with the magic `1.83` in CCActivity#setupFlexibleScreenMode - it's mentioned in the Device Resolution document and is the best fit after some experimentation. Ideally there would be a programatically derived scaling solution, but i'm unsure what to scale against.

Devices Tested
* Galaxy S4 GT-I9505G
* Tab 4 SM-T900
* Galaxy Note GT-N5110
* Galaxy S2 SGH-T989
* Kindle Fire HDX 8.9