to support dialect-level reflection options for all :class:`.Table`
objects reflected.

- Added a new dialect-level argument ``postgresql_ignore_search_path``;
this argument is accepted by both the :class:`.Table` constructor
as well as by the :meth:`.MetaData.reflect` method.  When in use
against Postgresql, a foreign-key referenced table which specifies
a remote schema name will retain that schema name even if the name
is present in the ``search_path``; the default behavior since 0.7.3
has been that schemas present in ``search_path`` would not be copied
to reflected :class:`.ForeignKey` objects.  The documentation has been
updated to describe in detail the behavior of the ``pg_get_constraintdef()``
function and how the ``postgresql_ignore_search_path`` feature essentially
determines if we will honor the schema qualification reported by
this function or not. [ticket:2922]

_reset_agent, so that it's local to the various begin_impl(),
rollback_impl(), etc.  this allows setting/resetting of the flag
to be symmetric.
- don't set _reset_agent if it's not None, don't unset it if it isn't
our own transaction.
- make sure we clean it out in close().
- basically, we're dealing here with pools using "threadlocal" that have a
counter, other various mismatches that the tests bring up
- test for recover() now has to invalidate() the previous connection,
because closing it actually rolls it back (e.g. this test was relying
on the broken behavior).

:class:`.RootTransaction` or :class:`.TwoPhaseTransaction`
with its immediate :class:`._ConnectionFairy` as a "reset handler"
for the span of that transaction, which takes over the task
of calling commit() or rollback() for the "reset on return" behavior
of :class:`.Pool` if the transaction was not otherwise completed.
This resolves the issue that a picky transaction
like that of MySQL two-phase will be
properly closed out when the connection is closed without an
explicit rollback or commit (e.g. no longer raises "XAER_RMFAIL"
in this case - note this only shows up in logging as the exception
is not propagated within pool reset).
This issue would arise e.g. when using an orm
:class:`.Session` with ``twophase`` set, and then
:meth:`.Session.close` is called without an explicit rollback or
commit.   The change also has the effect that you will now see
an explicit "ROLLBACK" in the logs when using a :class:`.Session`
object in non-autocommit mode regardless of how that session was
discarded.  Thanks to Jeff Dairiki and Laurence Rowe for isolating
the issue here. [ticket:2907]

events including auto-invalidation, which is useful both for tests here as well as
detecting failure conditions within the "reset" or "close" cases.
- rename the argument for PoolEvents.reset() to dbapi_connection and connection_record
to be consistent with everything else.
- add new documentation sections on invalidation, including auto-invalidation
and the invalidation process within the pool.
- add _ConnectionFairy and _ConnectionRecord to the pool documentation.  Establish
docs for common _ConnectionFairy/_ConnectionRecord methods and accessors and
have PoolEvents docs refer to _ConnectionRecord,
since it is passed to all events.  Rename a few _ConnectionFairy methods that are actually
private to pool such as _checkout(), _checkin() and _checkout_existing(); there should not
be any external code calling these

when a pre-DBAPI :class:`.StatementError` were raised within
:meth:`.Connection.execute`, causing encoding errors for
non-ASCII statements.  The stringification now remains within
Python unicode thus avoiding encoding errors. [ticket:2871]

Hide password in URL and Engine __repr__

pattern

Fixes #2821

instead of relying upon various ``quote=True`` flags being passed around,
these flags are converted into rich string objects with quoting information
included at the point at which they are passed to common schema constructs
like :class:`.Table`, :class:`.Column`, etc.   This solves the issue
of various methods that don't correctly honor the "quote" flag such
as :meth:`.Engine.has_table` and related methods.  The :class:`.quoted_name`
object is a string subclass that can also be used explicitly if needed;
the object will hold onto the quoting preferences passed and will
also bypass the "name normalization" performed by dialects that
standardize on uppercase symbols, such as Oracle, Firebird and DB2.
The upshot is that the "uppercase" backends can now work with force-quoted
names, such as lowercase-quoted names and new reserved words.
[ticket:2812]