[API change] no need for access to MarbleModel in RoutingRunners

* this is actually a follow-up on commit 830fa0809f0dfb6ba696554aa26a2a865cd9ff39
turn pointer into value
fix placemark tracking
disable position tracking if requested plugin isn't found
CurrentLocationWidget: show "No position available." when no plugin is active and "Waiting for current location information..." when waiting for a fix
make Placemark and RouteSimulationPositionProviderPlugins built-in

* having PositionProviderPlugin know about MarbleModel can be avoided by having these two plugins built-in
* for the satellites tracking feature there is even a hardcoded dependency on PlacemarkPositionProviderPlugin in CurrentLocationWidget
[API change] remove MarbleModel property from PositionProviderPlugin
fix path to marble.qrc
reorder slots
PositionTracking
merge methods
move exportGpx() from RoutingModel to RoutingManager
move rightNeighbor() from RoutingModel to RouteRequest
RoutingModel: don't pass a MarbleModel
forward route()
move updatePosition()
RouteGuidance