Fixed #18551 -- Enabled skipIfDBFeature/skipUnlessDBFeature to decorate a class

Thanks Tim Graham for the review and improved patch.
Fixed #20765 -- Set small values of `step` using exponential notation.

Browsers parse small factors of 10 as 0 under decimal notation.

Thanks to Trac alias matklad for the report and Claude Paroz for the review.
Fixed #13696 -- ensured inline pk field is rendered
Fixed an email validation regression

Thanks Vincent Wagelaar for the report.
Fixed #13629 -- Added CSS classes to the `<body>` tag of some admin templates to allow style customizations per app or per model.
Fixed #20781 -- Fixed _has_changed regression with MultiValueField

Thanks Tim Graham for the report.
Fixed #20773 -- [gis] Fixed regression in GoogleMap output

Thanks Martyn Clement for the report and the initial patch.
Fixed #19019 -- Fixed UserAdmin to log password change.

Thanks Tuttle for the report.