largefiles: improve help
Extension help taken from the URL formerly in the text
(https://developers.kilnhg.com/Repo/Kiln/largefiles/largefiles/File/usage.txt)
and improved.
largefiles: allow minimum size to be a float
Some old-fashioned people (e.g. me) think that incompressible
binary files >100 kB count as "large".
httpclient: update to
07d8c356f4d1 of py-nonblocking-http
This addresses a defect when the server closes the socket before
finishing a response (if it crashes, for example) first spotted in
Issue2951.
wireproto: do not call pushkey module directly (
issue3041)
Call the repos pushkey/listkeys member function instead.
So the pushkey-hooks are triggered.
largefiles: add beginnings of test (covers commit, remove, move, copy, and archive)