Simplified and refactored parts of init script

Simplified and refactored parts of init script

There is still much that can be done, but I will leave if or now, as it's not
really needed unless others use this framework, and that might not ever happen

It was still fun to do, and educational.

^_^

    initialize_project.sh
SDL_mixer fix so that it doesn't need patching

SDL_mixer fix so that it doesn't need patching
As of SDL_mixer update (hg:0237197714b6), the following local configuration
is enough to build SDL_mixer for android, such that fixes are no longer necessary.

    README.md
    android/jni/Application.mk