A Python API for the collision group / mask has been added:
The maximum number of collision groups and masked has been increased from eight to sixteen. This means that the max value of collisionGroup/Mask is (2 ** 16) - 1
EndObject will now activate objects that were sleeping and colliding with the removed object. This means that, unlike now, if a rigid body starts sleeping on top of another object, when the latter is removed the rigid body will activate and fall, rather than float midair as before.
Collision groups that do not intersect used to collide on the first frame. Now this has been fixed so that they collide appropriately.
Thanks to agoose77 for his help.