Improve definition of projects belonging to QtPositioning & QtLocation

This enables clean builds of qtlocation repo even if Qt3D is not available.
In such cases only QtPositioning related projects should be build.

There is a small build fix as well as some quick related includes
changed from proper includes to forward declarations.

Change-Id: Ifa8a9315beabcc1f64be219f8fa55236bf4ce42f
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Fix MapGestureArea consuming mouse events.

If MapGestureArea.enable == false, allow mouse events to be passed
on to the Map's parent item.

Change-Id: I9d7fc2ca760193e6b523565a7459612db927f909
Reviewed-by: Alex Blasche <alexander.blasche@digia.com>
Reviewed-by: Aaron McCarthy <mccarthy.aaron@gmail.com>