Add support for more resolutions

[vlidholt]

Add support for Android resolutions and export of images in 1.5x & 3x (phablet & phablethd?)

[NickyWeber]

yeeeha!

[haligalaph]

What about user's custom resolutions like in CocosBuilder? That was useful feature, I have no idea why it was removed. And there is no ability to have portrait and landscape resolutions in one project. Now I have to create two separate projects that share the same resources.