MacGui: implement a slider for deblock.

MacGui: implement a slider for deblock.
- Slider goes from "Off"  and then ranges from 5-15.
- Update preset code to handle the old bool for deblock where we convert "yes" to a value of 5.
- Note: though the deblock filter actually has a setting of 0, for the macgui we use an integer of 0, which shows up in the interface as "Off" to indicate not to load the filter at all. Made presets etc, easier to modify.

git-svn-id: svn://localhost/HandBrake/trunk@1750 b64f7644-9d1e-0410-96f1-a4d463321fa5