make sensorfw plugin handle the sensord restarting.

 This way, clients that are connected will continue to receive updates
 after the sensord has restarted, without the need to restart the
 sensor.

Task-number: QTBUG-34050
Change-Id: I4a8fbca189764cf23a1453feae5c1fd9ed6911e7
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
static linking: add classname to qmldir

The new qmlimportscanner for static linking depends on the
qmldir reporting the classname of the plugins. So add that
to sensors as well.

Change-Id: I80fd0a1d705ef589268231e6399f612a74b70828
Reviewed-by: Thomas McGuire <thomas.mcguire@kdab.com>
Merge remote-tracking branch 'origin/stable' into dev

Change-Id: I78c9a02406695ce145b93a46cfa60961e40fc2dc