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.

- fix the targeting of module names moved around by using custom handlers for "Bases", etc.

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

provides the functionality of query.with_polymorphic()
in a standalone form.   It can be applied to any
entity within a query, including as the target
of a join in place of the "of_type()" modifier.
[ticket:2333]
- redo a large portion of the inheritance docs in terms
of declarative, new with_polymorphic() function
- upgrade examples/inheritance/polymorph, rename to "joined"

"basic relationship" examples, cleaned up the examples and added
some more explicitness.  Also renamed "treenodes" to "nodes" and
added self-referential declarative example.
- Added info/examples on how to join tables directly when querying with
joined table inheritance.
-  Starting to talk about hybrids in the main mapper docs some more.
introducoed the idea that synonyms are on their way out.
- SQL expressions as mapped attributes also gets better verbiage,
alternative approaches to them, including hybrids.
- modernized the hybrid example.
- object_session() as a standalone function wasn't documented ?!

- converted all eager to joined in examples
- fixed beaker/advanced.py to reference RelationshipCache