CoordinateSpace

[Hugh Hoover <heh>]

Since tables have a coordinate space, shouldn't coordinate spaces be moved
from febe to xpp?

  Also, I'm building the initial tables with only 2 kinds of cs, integer
and heaperAsPosition.

  implication of coordinate space in tables:  a composite table can have only
one coordinate space - which is enforced during construction.  Seems
reasonable, I don't know what I'd do with a mixed one...

  A thought..  If you had a table with a set-ordered cs, wouldn't that
replace sets (or setbangs, depending on table)?  Main difference is
a streamlined protocol for sets.  Of course, the sematics are a bit different
for iterator(), count()... since they work on the contents of a position
rather than the positions.  So, having sets as a subclass of seftable isn't
quite useful.

--Hugh