Add refined movement and rotation controls

[An3Dev]

@chrisfd805 suggested that we should add a feature where holding down or pressing a button will reduce the motor speeds to make precisely turning and moving easier to control.

I think a potentially better way of doing this would be to bind one button to each action. For example, pressing the left controller paddle(or also the West button) can make the robot slowly turn counter-clockwise and pressing the right controller paddle(or also the East Button) can make the robot slowly turn clockwise.

@chrisfd805 and @Jtuazon25 let me know what you guys think of these ideas, and whether you want me to implement them.

[flynneva]

@An3Dev you guys are using an xbox controller for input right? Why not mimic video games and use the "crouch" button (clicking in the joystick) to slow down everything. That might be more intuitive for anyone who has played any of the major video game franchises since when you crouch you move a bit slower.

This can be done by adding a scalar variable to the movement speed and when the crouch button is pressed then the scalar variable is reduced which then reduces the final movement speed.

[An3Dev]

Forgot to close this issue. I added precision mode a few days before the competition.