Tray daemon stop / restart buttons

[bakkdoor]

Currently the daemon doesn't stop or get restarted. Need to fix that.

[lordi]

BTW For in-app daemon management, I did some work for this at https://github.com/syncrypt/elm-desktop/tree/daemon-management

[bakkdoor]

Can you merge that into master (or finish it and then merge into master)?

[bakkdoor]

We should hook into the daemon API correctly for starting/stopping/restarting the daemon here: https://github.com/syncrypt/elm-desktop/blob/master/static/main.js#L24-L60

I noticed that when the daemon is started directly by the desktop client then the stop/restart buttons work as expected, but if the daemon is started outside of the desktop client (or e.g. by an older version of the desktop client) the buttons don't work anymore. Both stopping and restarting the daemon fails. We should make sure this works regardless of how the daemon process was started.