manually merged exaples.

Change-Id: I9532d3b13d13f2769e6ca48eea23dd7d4041f68f
(cherry picked from commit e3bdd80c6661c0e95fb67998c57540be667ce761)

Change-Id: Id318122cb360b58604a658f3de1e5fce8b4a3e33

includes adjustment to setup.py to recognize __version__ correctly

remarkably, the examples for concrete and single were still
using classical mappings.    Ensure all three examples use
modern declarative patterns, each illustrate the identical set
of query operations.  Use back_populates, flat=True for joins,
etc. ensure flake8 linting, correct links and add a link back
from newly reworked inheritance documentation.

Change-Id: I8465a9badbb0eda804f457ccac599f051ee3c27c

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"