[1.7.x] Added release dates to release notes.

Backport of 9dc782b631 from master
[1.7.x] Bump version number for bugfix release.
[1.7.x] Post-release version bump.
[1.7.x] Added stub release notes for 1.7.2.

Backport of 4bf86d25e5 from master
[1.7.x] Added a warning about running migrations with DEBUG=True.

Thanks Charles Lanahann for the report.