ReconstructionManager::Write now uses the NumPoints3D as proxy for a reconstruction's size and writes the output in descending order based on size. This allows larger reconstructions to be written first which is a useful behavior since sparse models may end up with a large main recon and more much smaller ones, and with this change we ensure that if we only look at the first recon it will be the "main" one.

Co-authored-by: Antonios Matakos <anmatako@dss.microsoft.us>