Fixed #22397 -- Issues removing M2M field with explicit through model.

Changed the migration autodetector to remove models last so that FK
and M2M fields will not be left as dangling references. Added a check
in the migration state renderer to error out in the presence of
dangling references instead of leaving them as strings. Fixed a bug
in the sqlite backend to handle the deletion of M2M fields with
"through" models properly (i.e., do nothing successfully).

Thanks to melinath for report, loic for tests and andrewgodwin and
charettes for assistance with architecture.
Use the stdlib's PBKDF2 implementation when available.

This is a bit faster than ours, which is good, because it lets you increase
the iteration counts.

This will be used on Python 3.4+, and, pending the acceptance of PEP466, on
newer Python 2.7s.
Typo fix
For another day
Include an 'extra_requires' for bcrypt
Stray paren
Fixed #22456 -- Replaced 900913 EPSG code by 3857 in some tests

3857 is now the official EPSG code for the Google spherical mercator
projection and some recent versions of GDAL do not recognize 900913
any longer.
Thanks Tim Graham for the report and initial patch.
Confirmed support for PostGIS 2.1 and GDAL 1.10

Refs #22456.
Merge pull request #2583 from alex/extras-bcrypt

Include an 'extra_requires' for bcrypt
Merge pull request #2582 from alex/stdlib-pbkdf2hmac

Use the stdlib's PBKDF2 implementation when available.
Fixed a KeyError on login with legacy sessions; refs #21649.

Thanks Loic for the report.
Fixed #22444 -- Marked initial SQL/fixture loading as deprecated.

Thanks Karen Tracey for the report.
Fixed #22454 - Changed compatibility warning hint

The warning hint of `_check_test_runner` of 1.6 compatibility had a link
to a general release note. The link should be edited to refer the
relevant "Backwards incompatible changes in 1.6" section that documents
the cause and the possible solutions and workarounds of the warning.
Revert "Fixed #22397 -- Issues removing M2M field with explicit through model."

This reverts commit 00e3b9a2a992ee0b7288eeeb03e7cbd52ebc6dce.

It's causing a regression when tested with the proxy_model_inheritance tests.
Fixed #22464 - included contrib/gis/static in tarball

After switching to setuptools in commit 66f546b,
contrib/gis/static isn't included in tarball anymore, this commit adds
that path to be `recursive-include` in `MANIFEST.in`
Merge pull request #2586 from mmardini/patch-2

Fixed #22464 - included contrib/gis/static in tarball
Fixed a test failure introduced by 214d1e1b0f.
Merge remote-tracking branch 'upstream/master'
Fixed #22465 -- Fixes