Upgraded the turret.

- Added 5 new abilities to the turret.
* Speed, by right clicking on the block with glowstone dust, it will
fire 3 times faster.
* Fire, by right clicking on the block with flint and steel, it will
fire flame arrows.
* Damage, by right clicking on the block with gunpowder (subject to
change), it will increase damage dealt.
* All Mobs, by right clicking on the block with a repeater, it will
attack ANY entity other than yourself.
* Intelligent Shooting, by right clicking on the block with a
comparator, it will not attack tamed animals that you own (it will still
hit them if they get in the way, but will not target them)

- Updated fake-player to be invincible.
- Updated turret to allow empty shift-rightclick to empty all upgrades.