Fixed possible confusion.
If a command handler gets an error then the player will receive an unknown command error. This can be confusing for players.
HandleCommand now returns an CommandResult enum.
Added crBlocked and crNoPermission
(Force)ExecuteCommand returns the CommandResult enums
Exported and documented the CommandResult enums
Fixed multiple issues with projectiles

* Fixed arrows not being collectable/not truly hitting a block/not
lodging into blocks/not going in far enough
* Fixed projectiles not playing their block hit animation owning to
being destroyed too quickly
Some Entity.cpp style improvements
Bettered zombie and skeleton AI

* Fixed potential issues with skylight detection
Fix sheep color's, add shear sound.
Save IsSheared from Sheep.
Fixed doxycomments
An unification of code style
Code fixes.
Properly implemented enderchests
Removed bad comment
Suggestions
Unnecessary return
Add new hook: HOOK_PLAYER_FOOD_LEVEL_CHANGE
Add documentation.
Removed unneeded code
Implemented Vector3<>::Floor()