the MediaLibrary contains all of the media, but only gives access to the Clip, created upon the medias.
Cleaned metadata process: the clip doesn't appear inside of the mediaLibrary until the metadata process has been completed.
Removed junk/useless code

Removed debug

Solved missing icons for MediaProperty dialog

Basic start for medias's metatags. They're stored in the media, and displayed in the media property dialog

Cleaned MetaDataManager/Worker code, removed renderWidget, avoiding to permanent warning.

This reverts commit b99c1c6e.
There's a blocker which needs to be fixed first.

Added LibVLCpp::MediaPlayer destructor, avoiding event crashes
Fixed potential memory leaks
Removed junk code, corrected minor typo

Pause can be toggled until every single ClipWorkflow of every single TrackWorkflow has been paused.

This reverts commit df19117a.