to allow ad-hoc display of the source of any file, as well as a "directory listing" structure.
- reorganize examples/ to take advantage of new extension.  in particular, keep moving all
the descriptive text for files etc. into module docstrings, taking more advantage of
self-documentation.

- went through examples/ and cleaned out excess list() calls

can now provide "bind expressions" and
"column expressions" which allow compile-time
injection of SQL expressions into statements
on a per-column or per-bind level.   This is
to suit the use case of a type which needs
to augment bind- and result- behavior at the
SQL level, as opposed to in the Python level.
Allows for schemes like transparent encryption/
decryption, usage of Postgis functions, etc.
[ticket:1534]
- update postgis example fully.
- still need to repair the result map propagation
here to be transparent for cases like "labeled column".

- we don't have coverage for type-wide instrumentation events, the listener was broke.
could break again too.