Rebound Dash - experimental Sonic ability

[Reusable] Rebound Dash - experimental Sonic ability v15.1

Fixed a bug with simple mode and the input for short dashes. Thanks @SMS Alfredo !
- Added a challenge map: Rebound Training Zone. Test your skills and check out some of the level design potential!
- Increased Sonic's actionspd to 50
- Increased rebound height off walls
- Increased second bounce height multiplier
- Increased the amount of speed retained after rebounding off of a badnik
- Decreased Super Sonic's dash & rebound multiplier
- Restored Super Sonic's ability to float with the spin button
- Added new visual & sound effects to indicate that a second dash is ready to use
- Fixed a bug where simple mode could sometimes not use the dash's break function
- Improved solid object bounce angle detection - it should now be possible to graze the side of an object and bounce diagonally