Re-implement the /i command and make /give conform to the vanilla standards.

This commit is experimental and may fail. Please test it!
Cleaned up the code a little and fixed the messed up stuff that tried to make sure a player was good.
Removed some extra semicolons.
Kept the stuff alpha-sorted.
Added /item and made /i an alias of it.
Merge pull request #12 from mc-server/ireplace

Re-implement the /i command and make /give conform to the vanilla standards