Shadow dash implemented

Mostly changes to accommodate the new shadow dash. Did fiddle with the
phasing, though; collisions with the environment are now checked every
cycle for phasing, so it can be swapped on the fly.

~Shadow dash implemented. Hold the button to charge, release while
holding any direction to dash that way - including through phase-able
walls!
~Phase checking has been made more flexible, allowing for swapping
on-the-fly
~Fiddled with the numbers for hover, meaning the character floats up a
little higher