Set default chord as non-empty.

In order to give the users some hint what to expect from the app.
Fix the ProGuard config for Jackson.
Create a separate test project.

In order to prevent the build system to including the test classes and JUnit to the release APK.
Modify the pitch class namer to set the names via constructor and throw a runtime exception instead of just silently continuing.
Fix the ProGuard config for Jackson.