The VectorData generated was registered in the filter output,
thus creating problem when it was connected to other filters

BUG: fix #282 handler->getImageGeometry can return a null pointer on parsing error (here it was in ossimQuickbirdTiffTileSource)

ENH: modify SpectralAngleDataNodeFeatureFunction to output only the mean spectral angle along the datanode

* central region also defined with a radius
* neighboring region defined with 2 radius
* descriptor changed to output a value in [0, 1]

ENH: do not handle reprojection inside the filter, it needs a DEM if the image is in sensor model geometry

* make sure there is a == and != operator
* remove the 'const' from the non-static const members since they are not default-copiable