Playlist editor usability enhancements

[eric-gilbertson]

Playlist editor usability enhancements. Suggest the following enhancements to the playlist editor in order to streamline some of the common DJ operations (see attachment for example):

• add action menu to the right of the drag icon that supports insert above/below, track editing & track deletion
• add double click handler to track row that invokes track edit

One common action that these additions would simplify is the insertion of a track into the middle of an existing track list since they would eliminate the need to drag the new track to the target position which is a complex task.

[mapninja]

Reducing the number of clicks to delete an entry is a winner! Making the table view below directly editable would be super cool, too. Especially for repairing times, which happens often.