MacGui: Re-enable deleting encodes with the delete key if hilighted.

MacGui: Re-enable deleting encodes with the delete key if hilighted.
- Currently one at a time, multiple selections are shut off for queue sync reasons .
- Note: To delete a finished encode, click on it and hit your delete key ( since the action icon is an "open file in finder" magnifying glass) as this is the only way currently to delete a finished encode.

git-svn-id: svn://localhost/HandBrake/trunk@1744 b64f7644-9d1e-0410-96f1-a4d463321fa5