Object behavior improvements

[weluvgoatz]

Includes the following:

• [x] Rocks now bounce on trampolines and bumpers, as well as lessen gravity underwater and slide on slick ice.
• [x] Refactor and fix bugs for fallblock
• [x] Rocks should not crush Tux
• [x] Wind particles should appear properly
• [x] New option for script triggers, that has a script that plays when Tux touches the trigger and leaves the trigger
• [x] Icicle should not go behind switch
• [x] Improve wind
• [x] Add stop_sound() function Fixes #1782