the import structure of many core modules.
``sqlalchemy.schema`` and ``sqlalchemy.types``
remain in the top-level package, but are now just lists of names
that pull from within ``sqlalchemy.sql``.  Their implementations
are now broken out among ``sqlalchemy.sql.type_api``, ``sqlalchemy.sql.sqltypes``,
``sqlalchemy.sql.schema`` and ``sqlalchemy.sql.ddl``, the last of which was
moved from ``sqlalchemy.engine``.  ``sqlalchemy.sql.expression`` is also
a namespace now which pulls implementations mostly from ``sqlalchemy.sql.elements``,
``sqlalchemy.sql.selectable``, and ``sqlalchemy.sql.dml``.
Most of the "factory" functions
used to create SQL expression objects have been moved to classmethods
or constructors, which are exposed in ``sqlalchemy.sql.expression``
using a programmatic system.  Care has been taken such that all the
original import namespaces remain intact and there should be no impact
on any existing applications.   The rationale here was to break out these
very large modules into smaller ones, provide more manageable lists
of function names, to greatly reduce "import cycles" and clarify the
up-front importing of names, and to remove the need for redundant
functions and documentation throughout the expression package.

- change engine.Connection to _connection_cls so sphinx doesn't get upset
- globally add "." to all :class:`Foo`
- start naming sections that are mostly docstrings "API Documentation - blah blah"
- move some ad-hoc docstrings into "API" sections, there is some inconsistency here
and it may be that we just have to leave it that way
- add "internals" rsts to core, orm, I'm not super thrilled how these look but they are
targeted by some of the public api docs, users typically become aware of these anyway

  a consistent tag
- AUTHORS file

as well as "pool_logging_name" argument to create_engine() which
filters down to that of Pool.   Issues the given string name
within the "name" field of logging messages instead of the default
hex identifier string.  [ticket:1555]