1.2: More rappelling improvements

• Minor adjustments to rappelling sounds to improve timing
• Fixed issues with AR_Rappel_All_Cargo (editor-placed cargo groups now work and should support every heli)
• Reduced max rappel speeds. Action is only available under 100km/h. Players will fall from rope if heli reaches 150 km/h while rappelling.
• Added ability for pilot to rappel if engine is off
• Improved timing of AI rappelling (they don't all jump at once now)