Added the new flask-based hyrise docu theme

- custom favicon and new hyrise logo
- cleaned up locations of static files, moved all pictures into one directory
- new color scheme

- new flask-based layout, old themes are now deprecated
- new, responsive layout with static navigation for the whole documentation
- sidebar is resized according to window size
- highlight the current position in the docu in the sidebar
- restructured documentation folders for better maintenance (all rst files are now in /documentation)
- added new style for codeblocks, including the possibility to highlight syntax and show line numbers
- switched from explicit html code for static pages to rst layout (people)
- and more