Allow dragging of active track IF it is from the library column

[ColinRoitt]

When a track is loaded you cannot drag it between columns or in order. This is acceptable behaviour in live channels but the library becomes difficult to use when previewing a track, especially when there is only one item in the search results.

To resolve this tracks should remain draggable from the library when loaded in the preview player but not draggable from live channels when playing.

This code to amend is likely around here

[ColinRoitt]

Marking as enhancement as technically not a bug - please debate if we shouldn't add this.