[boosting] Use qt5 booster instead of generic one.
[dbus] Systemd file for dbus service so we get dependencies set.
Signed-off-by: Marko Saukko <marko.saukko@jolla.com>

It guarantees that the process will exit after 5 sec of inactivity.

createDownload() and createSync() calls don't need to explicitely reset the
timer because they always fire the statusChanged() signal which is wired to
exitSafely()

If TransferEnginePrivate::exitSafely() finds out that activity is still
ongoing it should cancel previously sheduled delayedExitSafely() call.
Otherwise delayedExitSafely() may be invoked between two syncs causing
nemo-transfer-engine to exit and get immediately restarted by D-Bus which
isn't something we really want. We want to exit when all the activity has
really calmed down.

The statusChanged() event is wired to TransferEnginePrivate::exitSafely()
which would otherwise think that something is still going on and wouldn't
exit, so transfer engine would keep on running forever. Which is what it
currently does.

Removed references to files, which are not in git.

When transferring multiple files via Bluetooth, we quickly receive
one transfer request after another, so this causes a timing issue
where the engine may quit immediately after the first request and
is in the process of closing down when the next request is received,
and thus cannot be started again for the next request.

Review fixes

MNotificationGroup::publish() sets its x-nemo-preview-body field
using the preview body of the last added notification group. This
means if the group is published before the notification, the
preview body used will be that of the last published notification
group instead of the current one.

If the group is published after the notification instead, the
notification will ensure the group properties are set correctly
before the group is published.

Allow MediaItem::ResourceName to be passed to sendNotification() when
MediaItem::Url is empty, as it will be if an uploader is sending a
non-file resource such as a vCard.