Revert "Removed code that cut off the last 25% of joystick motion in either direction. I'm not sure what the original purpose of this code was."

This reverts commit 4c34fb38.

Changed Joystick._exponential from bool to float. It can now be set between 0 and -0.5 by user using a slider.

Sensitivity of axis increases and deadband increases. This fixes an issue where the maximum percent output from an axis would be 100% - percentDeadband.

Removed code that cut off the last 25% of joystick motion in either direction. I'm not sure what the original purpose of this code was.