Garry's Mod JukeBox - YouTube Music Player

1. Video Checker popup changes:
2. Added checks to timed events to prevent errors.
3. Added JS function that should stop the video playing before closing.
4. Removed the ability to click on items in the YouTube player, preventing sounds from continually playing.
5. Added the ability to open the YouTube links in Steam Overlay rather than the popup for further inspection.
6. Added JukeBox.Settings.DefaultEnabled (defualt true).

There have been changes to the shared_settings.lua file, so the file will have to be replaced. Make sure to carry over your settings.