Allow individual file playback in Playback Queue or implement "Open in Finder" action

[joesawa]

Currently, when loading a combos.json, the "Play" button activates the viewing of all replays in the queue. It would be helpful to be able to select/double-click a single file to view rather than having to reorder the list.

Another possibility is to allow a user to double-click/right-click one of the .slp files in the queue and open a finder window to its location in filesystem.