become an externally usable package but still remains within the main sqlalchemy parent package.
in this system, we use kind of an ugly hack to get the noseplugin imported outside of the
"sqlalchemy" package, while still making it available within sqlalchemy for usage by
third party libraries.

for a select() element.  The "from" calc is now
delayed, so that if the construct uses a Column
object that is not yet attached to a Table,
but is later associated with a Table, it generates
SQL using the table as a FROM.   This change
impacted fairly deeply the mechanics of how
the FROM list as well as the "correlates" collection
is calculated, as some "clause adaption" schemes
(these are used very heavily in the ORM)
were relying upon the fact that the "froms"
collection would typically be cached before the
adaption completed.   The rework allows it
such that the "froms" collection can be cleared
and re-generated at any time.  [ticket:2261]
- RelationshipProperty.Comparator._criterion_exists()
adds an "_orm_adapt" annotation to the correlates target,
to work with the change in [ticket:2261].   It's not clear
if the change to correlation+adaption mechanics will affect end user
code yet.
- FromClause now uses group_expirable_memoized_property for
late-generated values like primary key, _columns, etc.
The Select class adds some tokens to this object and has the
nice effect that FromClause doesn't need to know about
Select's names anymore.   An additional change might be to
have Select use a different group_expirable_memoized_property
so that it's collection of attribute names are specific to
Select though this isn't really necessary right now.

- move testing.TestBase to test.lib.fixtures
- massive search and replace

local cls.Basic, cls.Comparable base class so that there is no ambiguity
or hash identity behaviors getting in the way of class registration.

access to the cls/self.tables/classes registries
- express orm/_base.py ORMTest in terms of engine/_base.py TablesTest,
factor out common steps into TablesTest, remove AltEngineTest as a
separate class.   will further consolidate these base classes

that don't ultimately have any Table objects referenced.
[ticket:1876]

make an alias() out of it distinctly.   This to eliminate
confusion over such issues as [ticket:1542]