Clean up OpenLayers directory

[nuest]

The OpenLayers directory contains documentation files and more, making the repo unnecessarily large! All files under doc and examples, probably also tests should be removed, also from the git history.

https://github.com/enviroCar/enviroCar-www/tree/master/assets/OpenLayers

[matthesrieke]

removing from the history will break every local repository as well as every fork. we should be aware of that.

[nuest]

Right... I guess right now we have only a few forks so it is (still) manageable.