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
An unification of code style
Suggestions
Implemented Vector3<>::Floor()
Vector clamping fixes

Thank you, @madmaxoft.
Suggestions
Eps comparison
Various fixed

* Fixed potential invalid pointer dereferencing, fixes #1117
* Fixed ender pearls not being loaded properly
Suggestions
Compile fix
Crash and compile fix
Changed everything to callbacks
Added extra space before comments
Merge pull request #1135 from mc-server/fixes

Fixes to projectiles and the undead