refactor/move-home-contents-to-guides

[wojciechkrzos]

The home contents are too long, which negatively impacts both readability and the way users perceive the documentation. The contents must be moved to the guides and kept to a minimum. Some guides like github, project management, and soon-to-be-added management and LTSP guides; already cover the home page text.

[dawidlinek]

Implemented in #30