Limited lines to 119 characters in django/{contrib,db}.

Refs #23395.
Fixed #23719 -- Fixed MySQL 5.6 crash with GeometryFields in migrations.
Forwardported 1.7.2 release note from a0cfd77971dc0e61427ca468e9b6ea9a548c796e.
Fixed #23614 -- Changed the way the migration autodetector orders unique/index_together

Thanks to Naddiseo for the report and Tim Graham for the review
Added cross reference in admin docs to topic about saving objects in formsets.
Fixed #23556 -- Raised a more meaningful error message when migrations refer to an unavailable node
Merge pull request #3280 from Markush2010/ticket23556

Fixed #23556 -- Raise a more meaningful error message when migrations refer to an unavailable node