Revert "[phys various] BodyDefs should be accessed through virtual method."

This reverts commit 4d7cfae9f740288290fc4ed973a238feb7057362.

Conflicts:
	modules/ent/inc/bipeds.h
[world] Manually specify tilemap bdf
[ent geo phys] Rename BodyDef to Object_Def
[phys various] Make set_def virtual
[ent shell] Replace Crate with generic Inert
[ent various] Inherit Biped_Def from Object_Def and make some fixes
[phys various] s/bdf/def
[various] Make new object def system work properly.