- add a connect=True key to connection record to support
  pre-loading of _ConnectionRecord objects
- ensure _ConnectionRecord.close() leaves the record in a good
  state for reopening
- add _ConnectionRecord.record_info for persistent storage
- add "in_use" accessor based on fairy_ref being present or not
- allow for the exclusions system and SuiteRequirements to be
  usable without the full plugin_base setup.
- move some Python-env requirements to the importable
  requirements.py module.
- allow starttime to be queried
- add additional events for engine plugins
- have "dialect" be a first-class parameter to the pool,
  ensure the engine strategy supplies it up front

Change-Id: Ibf549f7a1766e49d335cd6f5e26bacfaef9a8229

Co-Authored-By: Mike Bayer <mike_mp@zzzcomputing.com>
Change-Id: Ie6cf2d2958d1c567324db9e08fef2d3186e97350
Pull-request: https://bitbucket.org/zzzeek/sqlalchemy/pull-requests/80

back by using an attrgetter for the default case

be stated in the query string for a URL.   Custom plugins can
be written which will be given the chance up front to alter and/or
consume the engine's URL and keyword arguments, and then at engine
create time will be given the engine itself to allow additional
modifications or event registration.  Plugins are written as a
subclass of :class:`.CreateEnginePlugin`; see that class for
details.
fixes #3536