Move documentation from wiki to the code

[michael-batz]

At the moment, documentation is done in the yourCMDB wiki. This causes some problems especially the documentation of the behavior in different versions. A new documentation concept should be created which stores the documentation with the code and the specific version. The documentation should be also available on the yourCMDB webUI.

ToDos:

• [ ] create documentation concept
• [ ] create admin guide
• [ ] create development guide
• [ ] link documentation in yourCMDB webUI
• [ ] show documentation on the yourCMDB website