Follow Emacs convention for spacing after periods
magit-annex-file-action: Reformat docstring

The line is too long once a function name is added.
Refer to package names consistently

For each package, use the name and case that the package
documentation (most consistently) uses.  For this package itself, stick
with Magit-annex.
Clarify statement in commentary

All, not most, features are accessed through the popup menu.
Change package description
Add 'the' in front of 'annex'

This is consistent with the git-annex man page.
magit-annex-log-unused: Catch up with upstream

magit-log-refresh-buffer now takes a list of revs.  See Magit commit
5c0dc560f7d40f98b511a33e253499bed2a4d038.