Write documentation

[Gummibeer]

The whole documentation is missing and should be added.
It should cover basic usage but also have sections for every single component which describes it in detail for more advanced usage.

Every single improvement is welcome, so don't mind if you only add a single sentence or a whole section.
Atm the unittests are a good place to see some usage examples. But also the demo apps should get more content to look at.
If there are any questions I will ry to answer all of them.