Fix issues with non-interacting players

[Pugzy]

Not a clue what I'm doing with these patches to be honest but it works (I think).

Fixes two issues with "observers" i.e. players who are non-interacting using the ad() check.
For EntityLiving players this does a collidesWithEntities check and a parent ad which checks for !this.dead.

Prevents non-interacting players from stopping boat placement

• Entities with collision turned off will no longer prevent players from placing boats that would collide with them.
• This implementation also extends to other entities which do not have a hitbox.
  • This means that entities such as items and arrows also no longer block arrows (default in newer versions of MC) .

Prevents non-interacting players from being given armor from a dispenser

• Players in an "Observers" mode could stand in front of a dispenser and be given the items.
• Changes a method which uses !alive to the ad() which includes both a collision and alive check.

[cswhite2000]

Merged as part of #147