New experiment: capping cubes at weight 4

We’ve decided to start capping cubes at weight 4.

Currently cubes remain playable until they are declared complete.  This means that there are always available cubes for all players, but it also means that if a cube has not been declared complete it can keep growing indefnitely.  This creates problems when there are mergers in high weight cubes, and is inefficient for cube growth.

With the new cap, cubes will no longer be playable once they reach weight 4.  This should increase our efficiency for cell growth dramatically, and cut down on unremovable mergers.

For Science!