It was called MemSystem in the IDB because of a string in
ksys::InitializeApp that referred to MemSystem initialisation as
"Physics Memory System"; however that string actually referred to an
initialisation step for the physics system, not to the name of the
subsystem itself.
Also renames ContactInfoTable to ContactMgr because the contact info
table is a separate data structure that's managed by ContactMgr;
the manager itself handles more than just the table data
Léo Lam