lua: add example to rebuild the status line

This can be used to easily extent the status line for one's own needs.

I'm not experienced with lua so a few things could probably be done a
better way.
Implement 3 new properties

implements paused-for-cache, total-avsync-change and drop-frame-count properties

This is needed if you want to reimplement the status line in lua

I could only test drop-frame-count because I didn't find an easy way to
trigger paused-for-cache and total-avsync-change