Minimal support for Java editing

In Android applications, it is not uncommon to write some Java code to integrate with the system APIs. In Creator, there is no real support for writing Java code.

While creating a full blown IDE for Java is out of scope, we could make the experience better with a few small improvements:
1. Add a "Java file" type when creating a new file, so that people won't have to pick the "Generic Text File" type.
2. Verify that we are using the correct syntax highlighting (I think this is correct)
3. Fix automatic indentation (there are a few issues here, and probably one of the main things that make it difficult to use.)