[15] Fix Compilation errors further to review 2

- Update dependencies from umlgen.reverse.c to umlgen.c.common
- Update dependencies from umlgen.gen.c.common to umlgen.c.common
- Delete unused @Override
- Apply format configuration (this one is not freezed)
[15] Rename the folder of the plugin org.eclipse.umlgen.c.common
[16] Fix Legal notices are missing.

- Add about.html to the new plugins.
- Add the plugins to the feature.