Implement a basic Drag & Drop functionality to drag songs into the playlist
Add Drag & Drop for direct YouTube links

Fixes #10
Verify that the YouTube URL is an actual URL
Add some tests for the DirectYoutubeViewModel
Check against null
Implemented Drag & Drop moving inside the playlist
Show an indicator where the item in the playlist will end up when dragged
Make the playlist autoscroll when dragging
Merge pull request #85 from flagbug/drag-drop

Drag & Drop