add implementation of the rpc_model.direct_estimation_iterative function, to evaluate direct model (image to ground) even on dataset for which it is not provided (like the ones from DigitalGlobe).
add implementation of the rpc_model.direct_estimation_iterative
function, to evaluate direct model (image to ground) even on dataset
for which it is not provided (like the ones from DigitalGlobe).

dyoussef/s2p,jmichel-otb/s2p,jmichel-otb/s2p,jmichel-otb/s2p,dyoussef/s2p,MISS3D/s2p,MISS3D/s2p,MISS3D/s2p,MISS3D/s2p,dyoussef/s2p,carlodef/s2p,dyoussef/s2p,carlodef/s2p,mnhrdt/s2p,jmichel-otb/s2p,mnhrdt/s2p