More entity/camera path options

[ManDude]

• "Reverse" path option.
• "Shorten" path option.
• "Batch positions" option.
• "Interpolate positions" option.

Shorten should delete and reposition path points so it follows pretty much the same path but with less points (maybe it should shorten by % i.e. 100% means only 2 points: start and ending, and 50% just sort of removes half of the path points).

Add more if needed.