Bug fix: seg fault on selecting an new item when the previous was deleted.

Conflicts:
	src/GUI/ui/MainWindow.ui
	vlmc.pro

Add of a delete button on the media cell and an hightlight selection.

The selected clip wasn't updated.

The preview and the tag system are available again.
Some clean

Importing medias is available again

When a media is selected, preview widget shows the snapshot so the user is aware of which clip is going to be previewed.
Black background is now always shown, even when previewing.

Import refactoring stared, not over yet

Conflicts:
	src/GUI/MainWindow.cpp
	src/GUI/ui/MainWindow.ui

Add of a clip list inside a media.
This list can now be shown by the arrow in the MediaCellView. This arrow is a generic clickableLabel.

Please update vlc to the newest version

Removing the ugly hack to make the QSharedDataPointer doesn't screw the memory, because it wasn't that

We finally discovered where was this fu****g memory corruption bug, thx to Chouquette, I want also thanks my mother, my father and "Bernardmy pony

Conflicts:
	src/GUI/MainWindow.cpp
	vlmc.pro

bigger thumnails, no margin

Add the possibility to enable/disable the EffectEngine (but very Huglyly (is't a valid english word?), because it's temporary, just for demo and merge into master branch)