- merged #1401 branch from bitbucket

- merged #1401 branch from bitbucket
- resolved some serious speed hits I missed, we need to ensure
only deannotated columns are used in the local/remote collections and soforth
so that hash lookups against mapped columns don't dig into __eq__()
- fix some other parity mismatches regarding stuff from [ticket:2453],
including finding another case where _deep_annotate() was doing the wrong thing,
new tests.
- [feature] Major rewrite of relationship()
internals now allow join conditions which
include columns pointing to themselves
within composite foreign keys.   A new
API for very specialized primaryjoin conditions
is added, allowing conditions based on
SQL functions, CAST, etc. to be handled
by placing the annotation functions
remote() and foreign() inline within the
expression when necessary.  Previous recipes
using the semi-private _local_remote_pairs
approach can be upgraded to this new
approach. [ticket:1401]