[1.7.x] Fixed #23400 -- Added "Remove 'south' from INSTALLED_APPS" to upgrade instructions.

Thanks dgrant for the report.

Backport of bda2809712 from master
[1.7.x] Post release version bump.
[1.7.x] Added dates to release notes.

Backport of 0fd23545db from master
[1.7.x] Added stub release notes for 1.7.1.

Backport of 09c1f18f22 from master
[1.7.x] Fixed typo in docs/topics/db/transactions.txt.

Backport of 4db75925be from master