Fixed #23298 -- Made makemessages actually ignore specified dirs on Windows.

This was detected by two failures in the i18n.test_extraction of our
test suite.

Refs #20422, refs #22336
Stopped skipping GIS forms tests on MySQL
Fixed #23263 -- Added sqlmigrate to migration topic guide.
Fixed #23309 -- Fixed call_command to parse args correctly
Merge pull request #3075 from ramiro/makemessages-ignore-windows

Fixed #23298 -- Made makemessages actually ignore specified dirs on Wind...
Fixed #14638 -- Clarified model Field.to_python() docs.

Thanks Anubhav Joshi for the patch.
Fixed #23303 -- Added BEGIN and COMMIT statements to the output of sqlmigrate.
Fixed #23136 -- Added a message when sqlclear does nothing
Fixed flake8 warning.
Removed test, duplicate of admin_scripts.CommandTypes tests
Fixed #22171 -- Improved sanitize_separators cleverness

Thanks Klaas van Schelven for the report and Tim Graham for the
review.
Fixed some doc errors that caused syntax highlighting to fail.
Fixed #5726 -- Documented that inspectdb doesn't detect defaults.
Fixed #4991 -- Emphasized XSS ramifications of help_text not being escaped.
Fixed #23282 -- Corrected inheritance and reverse relations example.

Thanks knowledgepoint-devs for the report and claudep for review.
POC for #18757.

Make resolve_columns a permanent fixture, remove convert_values.

Current implementation passes on sqlite at least, but does destroy
performance. Need a nicer converter-collection based approach. Also some
tests that we can use the new override from_db_value, and that #21565 is
fixed in the process.
Fix some obvious errors.
Make sure gis' extra select fields are processed.
Making the pk non-concrete is weird.

Test seems to pass making the namefield non concrete instead, though
this may just be because there is no converter for CharField. Anyway
this is a weird way to do this test...
Need to tell mysql-gis backend to use gis compiler.