Improve the interface used by adapted drivers, like the asyncio ones,
to access the actual connection object returned by the driver.

The :class:`_engine._ConnectionRecord` and
:class:`_engine._ConnectionFairy` now have two new attributes:

* ``dbapi_connection`` always represents a DBAPI compatible
object.  For pep-249 drivers, this is the DBAPI connection as it always
has been, previously accessed under the ``.connection`` attribute.
For asyncio drivers that SQLAlchemy adapts into a pep-249 interface,
the returned object will normally be a SQLAlchemy adaption object
called :class:`_engine.AdaptedConnection`.
* ``driver_connection`` always represents the actual connection object
maintained by the third party pep-249 DBAPI or async driver in use.
For standard pep-249 DBAPIs, this will always be the same object
as that of the ``dbapi_connection``.  For an asyncio driver, it will be
the underlying asyncio-only connection object.

The ``.connection`` attribute remains available and is now a legacy alias
of ``.dbapi_connection``.

Fixes: #6832
Change-Id: Ib72f97deefca96dce4e61e7c38ba430068d6a82e

Also replace http://pypi.python.org/pypi with https://pypi.org/project

Change-Id: I84b5005c39969a82140706472989f2a30b0c7685

Fixed an issue that presented itself when using the :class:`_pool.NullPool`
or the :class:`_pool.StaticPool` with an async engine. This mostly affected
the aiosqlite dialect.

Fixes: #6575
Change-Id: Ic1e27d99ffcb20ed4de82ea78f430a0f3b629d86

Added support for the aiosqlite database driver for use with the
SQLAlchemy asyncio extension.

Fixes: #5920
Change-Id: Id11a320516a44e886a6f518d2866a0f992413e55

Log an informative message if a connection is not closed
and the gc is reclaiming it when using an async dpapi, that
does not support running IO at that stage.

The ``AsyncAdaptedQueue`` used by default on async dpapis
should instantiate a queue only when it's first used
to avoid binding it to a possibly wrong event loop.

Fixes: #5823
Change-Id: Ibfc50e209b1937ae3d6599ae7997f028c7a92c33

Change-Id: Ic5bb19ca8be3cb47c95a0d3315d84cb484bac47c

Change-Id: I4940d184a4dc790782fcddfb9873af3cca844398

Fixes: #5719

<!-- Provide a general summary of your proposed changes in the Title field above -->

### Description
Make it explicit in the documentation and in the default value for the 'timeout'
parameter that `timeout` can be a float. Because Python timing is not
very accurate, warn about the precision.

### Checklist
<!-- go over following points. check them with an `x` if they do apply, (they turn into clickable checkboxes once the PR is submitted, so no need to do everything at once)

-->

This pull request is:

- [ ] A documentation / typographical error fix
	- Good to go, no issue or tests are needed
- [x] A short code fix
	- please include the issue number, and create an issue if none exists, which
	  must include a complete example of the issue.  one line code fixes without an
	  issue and demonstration will not be accepted.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.   one line code fixes without tests will not be accepted.
- [ ] A new feature implementation
	- please include the issue number, and create an issue if none exists, which must
	  include a complete example of how the feature would look.
	- Please include: `Fixes: #<issue number>` in the commit message
	- please include tests.

**Have a nice day!**

Closes: #5710
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/5710
Pull-request-sha: 5f4eef8b4aba756d32e14ea41f71ef2919c26b84

Change-Id: I462524b1624ca5cc76d083a1d58e5dc89501c1a9

The following pool parameters were not being propagated to the new pool
created when :meth:`_engine.Engine.dispose` were called: ``pre_ping``,
``use_lifo``.  Additionally the ``recycle`` and ``reset_on_return``
parameters were not propagated for the :class:`_engine.AssertionPool`
class.  These issues have been fixed.

Fixes: #5582
Change-Id: Ifdb703aa7e849652242b9ff8071c854cd1d77e71