add to every modified function, method or class a real docstring

[utnapischtim]

the PR #17 added to every function, method or class which didn't have a docstring a docstring to fulfil the tests.

this should be fixed.

Due to the massive refactoring in the near future it is not necessary to add a valuable documentation to every function, method or class now. But every touched or modified function, method or class should have a meaningful documentation.