This freezes many things that normally happen automatically
in the world, including most ABMs and AISMs, and a few other
custom step logic items like the player "hot potato" logic.
This can be used for "creative mode" purposes to setup a complex
build without it running itself away from you, and for texture
pack authors, to have time to see things that are normally
transient or difficult to observe because of the effects they have
on nearby things or players.
This created a ton of dependency inversions, which
necessitated moving a number of API functions up into
higher layers, and restructuring dependency lists for
a number of mods.
BOLO: non-deterministic load errors due to missed
dependencies.
