GRIM: Don't draw the zbuffer of OBJSTATE_UNDERLAYs. Fix #143
GRIM: Find the sector with the exact name in MakeSectorActive().
GRIM: If setting a walk chore with no costume use the old chore costume. Fix #28
GRIM: Make Sector::getName() return a Common::String.
GRIM: Do not update the colormap two times for the same one.