* Read properties from unit interface only if it is valid and set a timeout
to prevent the UI from hanging
* Query the unit file state in case the unit itself cannot be queries so
the file state of disabled units with no status is shown correctly
* Reload unit status when starting a disabled unit with no status so the
effect is visible
* Lazy initialize systemd interface and don't initialize it
at all if the unit name is empty
* Allow to supervise/control system-wide units in addition to
user units (see https://github.com/Martchus/syncthingtray/issues/61)
* Avoid redundant code
Add new SyncthingLauncher class which lauches Syncthing
under the hood via external SyncthingProcess or using
libsyncthing.
Note: Launching via libsyncthing is still experimental.
* Only supported when Logind is used
* Extension of b2325bf
* So notifications caused by Syncthing inavailability
short after start or resume from standby can now be
suppressed - at least when using Systemd/Logind