Various work on Debian, OSX, and Windows stuff. Mostly uninteresting, but
took most of the day.

Made `git annex mirror --all` work. I can see why I left it out; when the
mirroring wants to drop an object, in --all mode it doesn't have an
associated file in the tree, so it cannot look at the annex.numcopies in
gitattributes. Same reason why `git annex drop --all` is not implemented.
But decided to go ahead and only use other numcopies configuration for
mirroring.

Added GETWANTED and SETWANTED to the external special remote protocol, and
that is as far as I want to go on adding git-annex plumbing stuff to the
protocol. I expect Tobias will release a boatload of special remotes
updated to the new protocol soon, which seems to prove it has everything
that could reasonably be needed.

This is a nice public git-annex repository containing a growing collection
of tech conference videos. <https://github.com/RichiH/conference_proceedings>

Did some design work on [[todo/untracked_remotes]], which I think will turn
out to be read-only remotes. Being able to clone a repository and use
git-annex in the clone without anything leaking back upstream is often
desirable when using public repository, or a repository with many users.
