Work/clang format preperation

@tbaumgart I think we could merge this already, then change the clang-format tooling if needed.

The tweaking also applies relatively well to the 5.1 branch.

The second commit came from reviewing the entire diff, took me a couple of hours but the most issues should be handled. Also did some improvements to the general coding style if they would also benefit the clang-format results. (The // at the end will preserve the linebreak when formatting).