Adds generators support for email backends that do not support it.
Fixed 20613 - moved pickle loads/dumps outside with self._lock.reader()/writer() blocks
Additionaly added pickled=None initially and check for none before
returning in get
Tweaked proj string regex in gis tests
Added release dates for gis libs as doc comments
[gis] Dropped official support for GDAL < 1.6
Fixed #14006 -- Documented that Field's 'description' attribute is interpolated with field.__dict__

Thanks abeld for the suggestion.
Fixed #20711 -- Fixed broken link in timesince.py docstring
Removed some logic that wasn't needed following removal of some deprecated code.
.DS_Store can be ignored.
Merge branch 'ticket_20613' of https://github.com/ersran9/django into t20613
A few cleanups to capture the minimum amount of code in try/except blocks.
Fixed #13813 -- Comparison of DatabaseWrappers doesn't raise errors.

Patch from Lukasz Balcerzak.
Merge pull request #991 from stockr-labs/feature/email-backends-generators

Fixed #20194 -- Adds generators support for email backends that do not support it.
Replaced some dicts with sets.
Fixed a bug I introduced in my previosu ommit.
A large number of stylistic cleanups across django/db/
fixed a mis-importt in mysql/base.py
Use a more explicit check for whether these ids are None.
Fixed #20625 -- Chainable Manager/QuerySet methods.
Added a test to ensure that the correct set of methods from `QuerySet` are copied onto `Manager`.