Enforcing nullability contracts in runtime

[denis-zhdanov]

This PR applies Traute to the project. The result is that Traute generates runtime null-checks based on NonNull annotations defined in source code.

Consider ATEUtils. applyTaskDescription() for example:

Source code

private static void applyTaskDescription(@NonNull Activity activity, @Nullable String key, int color) {
    ...
}

Resulting bytecode looks like if it's compiled from the source below:

private static void applyTaskDescription(@NonNull Activity activity, @Nullable String key, int color) {
    if (activity == null) {
        throw new NullPointerException("Argument 'activity' of type Activity (#0 out of 3, zero-based) is marked by @android.support.annotation.NonNull but got null for it");
    }
    ...
}

Raw bytecode

javap -c -private ./app/build/intermediates/classes/debug/com/naman14/timber/utils/ATEUtils.class
...
  private static void applyTaskDescription(android.app.Activity, java.lang.String, int);
    Code:
       0: aload_0
       1: ifnonnull     14
       4: new           #28                 // class java/lang/NullPointerException
       7: dup
       8: ldc           #29                 // String Argument 'activity' of type Activity (#0 out of 3, zero-based) is marked by @android.support.annotation.NonNull but got null for it
      10: invokespecial #30                 // Method java/lang/NullPointerException."<init>":(Ljava/lang/String;)V
      13: athrow
       ...