StockAbility Checker and small clean up

Check if there is already a stockability enabled or if there is one when
someone makes a new (fan made) ability. this allows you to create
ability with same name as default ones as long as you turn off the
default one. Also cleaned up some small parts, and will clean up the
command class in feature
FallingSand config!

Owners can now decide if bending affects fallingsand, there are 2 types
of fallingsand:
TNT and fallingsand, for both there are 2 config options if bending
should affect it, and if it affects it, than what should be the strength
multiplier be? 1.0 is the default strength and 0.1 is 1/10 of the normal
strength.

For developers:
new Methods, Methods.setVelocity(entity, vector)
Bad Commit, will revert
Revert "Bad Commit, will revert"

This reverts commit 30dbe6f2f71ba3a598b1fa086548219835e4bd7c.
Bad Commit 2, will revert.
Revert "Bad Commit 2, will revert."

This reverts commit 10801eb17501ba4f305f6a78d287d5715fcd7c93.
1.5.0 BETA 2
Unload Presets when a player signs out.
1.5.0 BETA 3