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
Add middle click.
Changed everything to callbacks
Added drop window action.
Added extra space before comments
Updated generator prefabs to current Gallery contents.
Merge pull request #1135 from mc-server/fixes

Fixes to projectiles and the undead
Added inventory number click.