Implement Migration.run_before

This attribute (used for reverse dependencies) was previously declared
and mentioned in the code, but never actually used.
Unicode method on model should return unicode

The example of a __unicode__ model method should return a unicode value
instead of a string.
Fixed #22384 -- Deprecated reversing URLs by dotted path.
Merge pull request #2756 from tubaman/return_unicode

Unicode method on model should return unicode
Removed erroneous trailing comma in OLMapWidget.js.
Updated current state of MySQL Connector/Python.
Added a patch review checklist.
Fixed #22681 -- Made TarArchive recognize leading directories properly.
Fixed #22717 -- Auto-corrected missing ending slash in FileSystemStorage

Thanks David Fischer for the report and Moayad Mardini for the
review.
Fixed #22684 -- Amended SelectDateWidget.empty_label to accept a tuple of values.

Thanks danielsamuels for the report
Fixed #13776 -- Fixed ModelForm.is_valid() exception with non-nullable FK and blank=True.

Thanks peterbe for the report.
Fixed #22747 -- Add backwards compatibility tip for new behavior of formset.save(commit=False).

Thanks django at patjack.co.uk.
Fixed #22710 -- Amended aggregation note for empty QuerySets

Thanks smeaton for report and Joël Rochat for spell check
Fixed RST syntax in 1.8 release docs.
Reordered setUp code in prefetch_related tests.

This allows these tests to run on databases that reject duplicate NULL
values in unique fields e.g. SQL Server.

Forward port of 4fb50a9a from stable/1.7.x.
Avoided using BinaryField unecessarily in tests.

Several database backends struggle with binary data. This change
minimizes the risk of unrelated tests failures when binary fields
trigger errors.

Forward-port of 2e4bcb9b from stable/1.7.x.
Added a flag for the ability to introspect nullable fields.

Previously this was conflated with another Oracle-specific behavior.
Fixed #22746 -- Removed background property from pre/code in admin CSS.
Fixed #21773 -- made daemon threads default in the development server.

Thanks clime for the report.
Fixed #10811 -- Made assigning unsaved objects to FK, O2O, and GFK raise ValueError.

This prevents silent data loss.

Thanks Aymeric Augustin for the initial patch and Loic Bistuer for the review.