Refs #20104.

As explained in ticket #20104, the use of versionchanged/versionadded
was confusing.

To solve this ambiguity these directives no longer accept a second
argument but now they only receive the version number (1st arg) and then
a content with the proper comment.

MergeDict evaluates now to False if all contained dicts are empty.
Thanks til for the report and the initial patch.

Refs #17840. Thanks Carl Meyer for noticing the omission.

Thanks cody.j.b.scott@

Thanks bmispelon.

Thanks jim at hellolocals.com for the report.

Thanks to mossplix for the review and bmispelon for the review.

The OGRInspectTest.test_time_field does still not succeed with these
databases (even when removing the postgis guard), but at least it's now
possible to setup a datasource.

Refs #20260.

Thanks to feraudyh at yahoo.com for the report.

Also, use Django templating for the dynamic generated JS code and use
more idiomatic coding techniques.

Thanks Matthew Tretter for the report and the patch.

Also fixed plural messages for DecimalField.

I refactored RadioSelect and CheckboxSelectMultiple to
make them inherit from a base class, allowing them to share
the behavior of being able to iterate over their subwidgets.

Thanks to Matt McClanahan for the initial patch and to
Claude Paroz for the review.

Thanks gsavix for the suggestion and patch.

Thanks burton449geo at gmail.com for the report.