JumpControl() function

moved code in Movement() to JumpControl() to keep things modular.
commented built-in OnCollisionEnter2D() functionality for my own
GroundCheck() function. Not sure which is better: line casts, ray
casts, or OnCollision__2D()
created Movement2() for more precise control, i.e. without using
rigidbody2D, not sure if I'll keep it, but the slide kind of sort of
works (See Test scene)