Added `git-annex-shell notifychanges` command, which uses inotify (etc)
to detect when git refs have changed, and informs the caller about the
changes. This was relatively easy to write; I reused the existing inotify
code, and factored out code for simple line-based protocols from the
external special remote protocol. Also implemented the git-remote-daemon
protocol. 200 lines of code total.

Meanwhile, Johan Kiviniemi improved the dbus notifications, making them
work on Ubuntu and adding icons. Awesome!

There's going to be some fun to get git-annex-shell upgraded so that the
assistant can use this new notify feaure. While I have not started working
on the assistant side of this, you can get a jump by installing today's
upcoming release of git-annex. I had to push this out early because there
was a bug that prevented the webapp from running on non-gnome systems. Since
all changes in this release only affected Linux, today's release will be a
Linux-only release.
