Slides, Wall Jumping and Grapple Hook Fix

* Added wallNormal variable which stores the normal of the last
collision made by the player that was too steep to climb.
* Temporarily implemented walking/running to increase speed instead of
setting it. This will need to be reworked for analogue.
* Created a wallAnchor with a similar function to the normal anchor.
This pushes the character towards walljumpable walls. Without it,
walljumping failed inconsistently.

* Bug Fix: When falling and touching a wall too steep to climb, the
character no longer halts momentum, and instead slides down.
* Bug Fix: Grapple hook now collides with walls (had to make it a rigid
body to do this).
* Bug Fix: Wall jumps now push the player away from the wall.