REVIEW: 118720

Resolve conflict in ClipPainter class: avoid shadowing the setClipping()/hasClipping() method.
- Cleaned up and refactored the AzimuthalProjection and GnomonicProjection.
- Turned GnomonicScanlineTextureMapper into a GenericScanlineTextureMapper.
- Got rid of all remaining projection specific code that used viewport->projection.
- Moved the Gnomonic projection to the right toolbutton menu.
- Prepared for further inclusion of "spherical" projections.
- Fixed a crash bug in the GnomonicProjection that would result from another
  division by zero.
Add Stereographic Projection and tests for it.
http://en.wikipedia.org/wiki/Stereographic_projection
This commit shows how easy it has become to add further projections
and can be used as a template for future additions.
I'm thinking of adding the vertical perspective projection next.
Add test for Stereographic projection for real.
Adjust the StereographicProjection test to be more forgiving.
avoid RouteRequest::pixmap() calling itself
REVIEW: 119225
Replaces PhotoOverlay visualisation on the globe with a Google Earth like.
This means it shows the icon of the overlay's style on the globe and shows
the actual image after click in a popup.
streetview