Remove Vagrantfile and related files

It seems to clutter this project and belongs somewhere else.
Move source files to the top level of the project

They are the main attraction. The Git project does it like this, too.
Remove example file, it probably belongs somewhere else
Fix the mpv-nordlicht.lua script: Start fullscreen after 0.1 sec.
Add "column" style
Allow the specification of a multi-track layout in API and CLI

You cannot spefify the track's heights yet, but this closes #27.