Update style in generate_java.*

- Add license notices
- Adopt Google style conventions
- remove string append(char* a, char* b)
- remove using std::* declarations from headers
- do not sprintf into a char buffer any longer

Bug: None
Change-Id: I42d95d25a6a88e87150bd9c7f1b79e26b9076c11
Test: compiles, unittests continue to pass
3 files changed