- fixed AVPlayer not restarted when transcoding already finished
 - TODO: Fix seeking in paused state results in resuming playback

 - still unstable and buggy
 - TODO: fix slow-motion-like playback when seeking a paused video

 - very poor stability and ui response time

 - still not working
 - seems that the second ok for signalling enough data available is not
   sent

 - the pause/resume buttonn will be disabled while a pause/resume action
   is in progress

 - Don't use the nVidia GPU on optimus devices for the application if
you have an GeForce MX GPU, because they don't have any video de-/
encoders and the application selects the encoder based on the rendering
GPU

This reverts commit 08df9c70.

 - Encoding is not possible in order to some bugs in the QtAV library

 - fluent slider movement kinda fixed (not completely fluent, but almost; no priority)
 - control playback position missing

 - fluent slider movement missing (kinda choppy)
 - control playback position missing