MultiBert EndSets

[Eric Dean Tribble <tribble>]

Marcs's worry about remembering the reference context when making a
link led to the "Stamp Out PartKeys" idea.  We came up with the same
solution.  SubStamps were insipred by noticing how little the
implementation cared whether Berts or PartKeys were recorded in the
context-path tree.  I suspect that the differences between reference
vs contained context information will vanish when we finish the
SubStamp extension.  If you think about the structures to be stored in
the containment vs reference context-tree, the containment tree just
has SubBerts and SubStamps where the reference tree has Berts and
Stamps.  It will just be a frontend function (:-)) to determine how
much context information to store, and how much to use when links are
followed using context information.  

We shouldn't have any trouble storing TableTop information as context,
when we decide to build tableTops.

dean