Check documentation folder for copyright issues

[bmehner]

During the SMC a lot of documentation was gathered and copied to the documentation folder. The copyright obligations related to this were never checked, I guess. So there might be a couple of issues here.

We should decide which documentation is still needed and which can be deleted. The documentation which is still needed should be checked whether there are copyright issues or if it can be replaced by other means (e.g. link to existing stuff on the web).