Gravity Control: FIX (for alex's caves and ars nouveau, maybe more)

1.3.5: adds better mob interaction with portals that modify gravity.

This mod requires Gravity Control by Tfarecnim:
https://www.curseforge.com/minecraft/mc-mods/gravity-control/files/6478254

There's a glitch with the original mod where if you have Alex's Caves, you can't land properly with altered gravity, this mod fixes that issue.
It also adds compatibility with Ars Nouveau's spells, specifically things like "Underfoot", projectile trajectories, etc.
Neither of these mods are required.
I will likely add other compatibilities to this later on if issues arrise.

I have done a lot of testing, but I haven't tested quite a lot, so please let me know if there are any issues right away and I will do my best to fix them.

Ars Nouveau tests: 
Leap working, projectile trajectory normalized, double jump from jump ring working, levitation belt working.
underfoot working.

Other fixes:
Rotation is based on player's head position, not feet position - so when you flip gravity, you stop burying your head in the floor and taking suffocation damage.

Gravity direction is preserved when switching dimensions, no weird half-remembered gravity direction where the player appears to walk and jump normally, but fires projectiles in the wrong direction and takes constant suffocation damage.

1.2.1 patch: Fixed a bug where the "burying head" compensation was incorrectly applied to gravity modified portals, causing immersive portal rubberbanding to offset too much and bury the player.

1.2.4 patch: Fixed a bug where a falling mob got an incorrect flip-anchor, resulting in buried mobs, this patch also fixes a bug where mobs rubberband between two immersive portals, resulting in mobs getting stuck inside portals or sometimes bypassing portals completely.  (added interaction delay to portals)