[PEAK] Proof-of-concept Trellis algorithm in SVN

[Phillip J. Eby]

Rather than try to explain all the details of my changed Trellis 
algorithm ideas, I just implemented them instead.  :)  The result is 
not adequately tested by a long shot (in particular, no *new* 
features are tested), but it passes all of the old tests that have 
been in SVN since I last worked on this about a year ago.  (Well, all 
of them except converting static cells to Constants, which I haven't 
decided how to handle in the new design just yet.)

That the new, from-scratch algorithm so readily passed the tests from 
a year ago is a good sign, especially considering that the code is 
also more compact and simpler and has additional features.  (Well, it 
has additional features in *theory* -- they're not actually *tested* yet.)

Anyway, if you want to feast your eyes on the glory that is the new 
algorithm, see here:

    http://svn.eby-sarna.com/Trellis/peak/events/trellis.py?view=markup

Of course, the *real* glory will be when the new features are tested 
and I add stress tests from Cells and PyCells, especially the old 
"pentagram of death" test.  We'll see how things work then, for sure.  :)

Btw, this version does NOT have any of the nice decorators I've been 
using in my API examples; those will get added after the basic Cell 
objects have been thoroughly vetted.  (The decorators and Component 
class will basically just be machinery to create properties for you 
that map to Cell objects so you don't have to do it by hand.)