Merge branch 'frontend-rewrite' into develop

first skeleton
static files can now be served from frontend/public
can now parse and return json, basic routes are there
added vlc.py from git.videolan.org (GPL >= 2.1)
basic skeleton for further threading
Youtube videos aswell as normal videos may now be played

via POST requests on /api/open, documentation to follow
Merge branch 'backend' into develop - basic playing functionality
Merge branch 'frontend-rewrite' into develop

first ui elements
GET on /api/status works a dictionary, to be documented
Merge branch 'backend' into develop: GET player status
Merge branch 'develop' into frontend-rewrite
slider gets updated by status