Added incoming rate limit preference.
Added compression preference to node settings.
Do not immediately finish() activity after creating or deleting repo/node.

This caused problems with restart dialogs ("activity has leaked window").
Instead, the activity is finished anyway as soon as the syncthing API
becomes unavailable due to restarting.

We will have to revisit this when syncthing does not need to be restarted
any more.
Dismiss "disabled" dialog when syncthing is available again (ref #127).
By default, sync under all conditions (ref #127).

This is so the user knows *why* syncthing disables itself.