Prefer android and android-library plugins before searching for other derivatives.

I was having some issues using the 'android-apt' plugin caused by the plugin detection code. I think it was accidentally selecting 'android-apt', rather than the actual android plugin. I changed the logic to prefer the 'android' and 'android-library' plugins, but search for other plugins as a last resort. I also refactored the code a bit to make it more clear on what's going on.