Refactor gh-pages into tutorials

[erleben]

Currently, gh-pages is set up to document code in a way similar to pep8/Doxygen type of documentation. The process is manual, and a bit redundant since the documentation already exists in code. Hence, it does not offer a lot of extra help to end-users.

Instead, there is a need for tutorials that explains how to use our code. That is on the level of modules and sub-modules. Information that shows code examples that one can quickly copy-paste from, explanations of the design ideas behind the code, good advice for best usage, and possible discussions of DO and DONT aspects.