Experience orbs merge too slowly

Experience orbs have been changed so they can consolidate if in proximity to each other. However, this consolidation is too slow to be useful in reducing entity lag caused by experience orbs.

To reproduce:
1. Create a new world.
2. Load the structure "xporbs" which loads a structure consisting of a redstone mechanism with 36 dispensers full of XP bottles.
3. Enable the mechanism to spawn XP orbs -> the XP orbs build up very quickly and don't consolidate quickly enough to be useful.