Added missing `versionadded` for `FormMixin.prefix`.
Fixed #20311 -- Make sure makemessages doesn't create duplicate Plural-Forms .po file headers.

Thanks naktinis for the report and initial patch.
Fixed a very old email address of mine still lingering in the AUTHORS file
Fixed errors and inconsistencies in CBV topic documentation.

The code examples should now work correctly.
The `get_context_data` method in the examples was changed when
necessary to adopt a singular style (get context with super(...),
add the extra keys to the dict then return it).

Thanks to Remco Wendt for the initial report and to Tim Graham
for the review.
Fixed #20524  - Described keywords in triaging contrib doc.
Corrected minor typos in FileUploadHandler.receive_data_chunk docs.