Pistons warp entities too much (Pistons pull entities in/through blocks)

Since the recent changes to block 36, entities that get pushed get set right in front of the block 36 collision box.
That makes sense, but it should only happen for entities which collision box is (almost) fully in front of the block 36.
Otherwise entities that just barely reach inside the block 36 from behind get warped in front of it.

Steps to reproduce:
1. Build up 2015-09-18_23.35.57.png
2. Remove the redstone block 2015-09-18_23.36.12.png
3. Place the redstone block
4. The armour stand got warped on top of the half slab 2015-09-18_23.36.19.png

This behaviour is kind of cool for the technical community, but it doesn't look intended, so better fix it fast before we get used to it

Making pistons work perfectly is a bit trickier than I though. I had a fix here, but it wouldn't have worked well in some cases either. So for now here is a list of points that might help:

• block 36 should use the list of collision boxes the block it holds has (currently it's just the rendering hitbox, I believe)
• to the outside block 36 probably should give of the hixbox it would have after finishing the current step, otherwise block-air-block can cause an entity that stands in the air block to get stuck on one of the block 36 and therefore getting inside the other block
• block 36 should only move entities in front of it, not all intersecting
• cauldrons should be able to keep a mob inside while moving (this is a good test if the code is working in the most difficult cases)

Hopefully I will get to update this to more useful info soon.