This is a new navigation mode for QgsCameraController which is meant to work
just like the terrain-based navigation mode, but for 3D scenes with globe.
Initially, the new navigation mode can handle:
- zooming in/out with mouse wheel
- orbit around globe when dragging with left mouse button pressed
- left/right/up/down keys to orbit around globe
- shift + left/right keys to change heading angle
- shift + up/down keys to change pitch angle
- page up/page down keys to increase/decrease elevation
For camera pose, we use QgsCameraPose as for "flat" scenes, but the QCamera
is positioned/rotated slightly differently - the main change is that in case
of globe, we use ECEF coordinates of the camera pose's center point, convert
them to lat/lon coordinates in order to set up initial rotation of the camera
so that it is perpendicular to the tangent plane at the given ECEF coordinate.
