Entities with NoAI:1 have collision and push the player

In the snapshot 15w36a, the entities were made so that they're able to push other entities. However, this collision property is present even when entities have AI disabled, this means, have the NoAI tag set to 1. This is most likely not intended, since that entities with AI disabled shouldn't be able to interact with the world in any way.

This causes issues with redstone machines that depend on the lack of world interaction to work. For example, if an invisible villager is teleported to the player for right-click detection, the player will be automatically pushed all the time, due to the collision with the villager.

This could easily be resolved with the addition of a NBT tag allowing the removal of collision. Otherwise, just disabling collision for mobs with disabled AI would also work. It is not possible to provide screenshots of the issue, so follow the steps below to reproduce the bug.

Steps to reproduce:
1- Summon any mob with the NoAI tag set to 1. (Suggestion: /summon Villager ~ ~ ~ {NoAI:1})
2- Try walking towards the mob.
3- You'll collide with the mob and it will be able to push you, even though it doesn't interact with the world in any other way (even gravity doesn't affect it).