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
Fixed doxycomments
An unification of code style
Suggestions
Implemented Vector3<>::Floor()
Initial codegen for LuaState_Call.inc.
Tolua generates LuaState_Call.inc file.
Vector clamping fixes

Thank you, @madmaxoft.
Suggestions
CMake: Changed slash format to support MSYS.

Ref.: #1044
Changed OnWeatherChanging hook to always read the returned weather.

Ref.: http://forum.mc-server.org/showthread.php?tid=1512
APIDump: Updated OnWeatherChanging docs after latest code changes.
Removed world-saving log messages.

Ref.: http://forum.mc-server.org/showthread.php?tid=1518
Fixed c1deda5d8f01811efa5094e9375166acb69d50ed

I keep on breaking stuff :P