Implement Track Rendering

[adam-ce]

The following things need to be addressed before we can merge:

• [ ] please revert the changes to deploy.yml (no need to increase the file size, the opengl timers are not working anyways, jakob)
• [ ] replace FileDialog with sth home grown in order to avoid QtQuick.Dialogs and widgets (Adam)
• [ ] work on api design, multiple tracks, track deletion (Adam)
• [ ] gl_engine/Window.h/.cpp are fully changed files. sth went wrong, probably with line endings etc (Jakob)
• [ ] copyright is missing in intersection.glsl (Jakob)
• [ ] use uniform buffers, and store to url / disk ? (Adam)
• [ ] move nucleus/gpx to nucleus/utils/gpx (jakob)
• [ ] remove dependency on iostream (doesn't work on android). print these things to qdebug or qwarning (jakob)
• [ ] move test gpx tracks to qrc (Adam, or Jakob if you want)
• [ ] copyright is missing in about qml (Jakob)

[gue-ni]

I improved some more things, is there anything else missing?