add empty examples/__init__.py

Needed for demo.py.
fix import paths for all_tests.py
add missing tests/__init__.py
fix parser

Add capabilities to the parser ... these are just the parser/AST changes, with full implementation to be done in a future commit.
Add 'provenance', 'signature' to func defs.
Add 'where' to func defs.  TBD how to handle 'where' for class/interface.
Add 'parents' to interface/class defs.
Changed 'raises' to 'raise' in function definitions, to minimize new reserved wrods.
Turn off tests for representation equality (not needed because of Eq capability).
simplify parser

Change parser to build the tree by adding new nodes that don't modify anything below them in the tree.
  e.g. p[0] = p[1] + [p[2]] instead of p[1].append(p[2]; p[0] = p1
Get rid of PyOpt{Func,Class,Interface}Defs because they only encapsulate a single list and add no value (but do add clutter).