stand/lua: Reduce exposure of the drawer module

As part of an effort to slowly reduce our exports overall to a set of stable
properties/functions, go ahead and reduce what drawer exposes to others.

The graphics should generally not be modified on their own, but their
position could be modified if additional grahics also need to be drawn.
Export position/shift information, but leave the actual graphic local to
the module.

The next step will be to create a 'menudef' that gets exported instead, with
each entry in the menudef table describing the graphic to be drawn along
with specific positioning information.