Reverted GlobeView change.
Turned centers back on in screen space builder.
A bit more guard code for the missing screen space generator.
Merge branch 'develop' of https://github.com/mousebird/WhirlyGlobe into develop
Wasn't taking offset into account for new markers.  Added a workaround for back geoC coordinates.
Simplified the fragment shader for screen objects.  Fixed a sampling problem in dynamic textures.
Upgraded lofted polys support to include vector centers.