MacGui: New queue enhancements

MacGui: New queue enhancements
- clean up work related to starting and stopping of jobs to make sure the behavior is the same in both the queue window and the main window
- No longer adds jobs to queue when you've hit Start but then canceled the overwrite warning.
- Added overwrite alert when doing an Add to Queue. Was only happening previously when you did a Start.
- Stopping a job from either the Queue window or the Main window now goes through the same code path and so the behavior will be identical.
- In the main window, the Start button now changes to Start Queue once you've added things to the queue. This helps clear up any ambiguity about what that button will do
- Cancel button now named Stop. Recommended by BradleyS and/or hawkman I think because this button no longer cancels everything in the queue, just the current job. Wording in the stop warning dialog has been improved (mentions job title).
- The "Show Alert When Done" options now work when you have started the queue from the Queue window.
- Uses the term "passes" in main window
- Added unique icons for each pass type.

git-svn-id: svn://localhost/HandBrake/trunk@949 b64f7644-9d1e-0410-96f1-a4d463321fa5