`android_base`: Easy graphics development on android using rust

Introducing android_base, a way to easily get started developing graphical application on android without having to worry about android-specific details or caveats. This takes care of crate versioning too, so what used to be a nightmare getting old versions of crates to comply with eachother is now easier as this prelude imports (I believe that's the right name, correct me if I'm wrong) the right version of pistoncore-graphics and other things which are needed to get started.

This also comes with a bit of a guide on how to go from regular rust development to android development using android_base


I've migrated my snake game to android_base and have simplified the code substantially!