Fixed #19746 -- Allow deserialization of pk-less data
Loaded cycle and firstof from future in built-in templates. Refs #17906.

This was missing from f49e9a517f2fdc1d9ed7ac841ace77636cbd6747.
Merge pull request #717 from slurms/ticket_19746

Fixed #19746 -- Allow deserialization of pk-less data
Test case and docs for custom context data in feeds

Thanks Paul Winkler for the initial patch. (Ref #18112).
Added a note about Feed.get_context_data to the 1.6 release notes.