mass clean up and bring back default config

This issue is mainly to explain why many other things should be done first before bringing back the default checkstyle configuration. To recap, there are around 7000 issues with the default config. Fixing those should be as efficient as possible, and should not lead to contradictions with how the Eclipse IDE works where the eclipse-cs source is developed (because otherwise we may play ping-pong between Eclipse formatting something, Checkstyle complaining, manual fixing, and repeating the cycle all over).

- [ ] Merge as many open PRs as possible. They would be in git conflicting state with all the reformatting changes coming later.
- [ ] Enable automatic import organizing. Modify settings to match Checkstyle rules. Run organize imports on all sources.
- [ ] Search/replace all the $NON-NLS markers in source code. Those are needed only for plugins which use bundle localization, which isn't the case for eclipse-cs.
- [ ] Enable auto-format on save in Eclipse. Right now the formatter is not active at all, therefore newly written code doesn't fit the Checkstyle settings (like line length). Modify formatter settings to fit Checkstyle settings. Format all existing sources using the Eclipse formatter.
- [ ] Enable cleanup on save in Eclipse. Enable as many options as possible. Run the cleanups. (Those cleanups work like automated refactorings. E.g. foo.equals("const") will automatically be reordered, thereby automatically fixing the Checkstyle issue.)
- [ ] ... maybe more coming up along the way
- [ ] enable standard config again, hoping the number should have gone down drastically