AndroidMidiTest moved to AndroidMidi module, project restructured to new Android conventions

[tkirshboim]

I've done some more restructuring to conform to the new Android project structure conventions and also allow building all of the projects contained in this repository with the new gradle build system. These changes include:

• Changed the folder structure of the AndroidMidi project to the current convention - The main reason for doing this was to allow running the java junit tests from 'AndroidMidiTest' using the Android gradle plugin.
• Moved the 'AndroidMidiTest' java junit test module to the 'AndroidMidi' module.
• Added all the modules contained in this repository to the root gradle project. Running ./gradlew assembleRelease will now build all of them, not only AndroidMidi.

It is now possible to run the tests by running ./gradlew test from the command line or in Android Studio (For that note that you should click the 'Build Variants' tab and there select 'Unit Tests' as the test artifact).

While running the tests, some tests in 'SystemMessageEncoderTest.java' failed. I'm not familiar with the code itself, so I'm not sure if this is a 'real' failure or perhaps a misconfiguration of the mock instance. I also don't know when was the last time that these tests passed, this is the first time today that I tried to run them. See the attached result:
TestResults.pdf

[tkirshboim]

removed 'MidiPlayer/src/META-INF/MANIFEST.MF' file that broke the debug build of the MidiPlayer app