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
Added the Lua Proxy DLL.

This builds the lua5.1.dll file on Windows, making it 64-bit if so required.
Added a missing endline.
Removed the md5 library, obsoleted by PolarSSL.

Fixes #1130.
Added PolarSSL dependency to Bindings.
Fixed server forcing players afloat

* Fixes #1131
Fixed bad water/redstone simulator communication

* Fixes #713
Minor change to buttons and levers

+ They now detect if the block they are on occupies its voxel, instead
of just being solid
Added more block exceptions to torches
Changed include folders to work for Bindings, too.
CMake: Added polarssl include dir as non-system.
Fixed a silly path error in #include.
Implemented tripwire(s) (hooks)

* Fixes #944
Fixed issue with breaking blocks at -1 coordinates