Use `LOOKUP_SEP` in `get_or_create`.
Fixed #20282 -- Typo in WSGI docs.
Fixed #20286 - Typo in static files docs.

Thanks bmispelon.
Fixed #20285 - Added missing commas in translation docs.

Thanks cody.j.b.scott@
Complemented documentation following commit be9ae693c

Refs #17840. Thanks Carl Meyer for noticing the omission.
Fixing #20276. MergeDict should have __nonzero__ / __bool__ properly implemented.