OpenSfM: Added Manifold support to export_colmap
OpenSfM: Added Manifold support to export_colmap

Summary: - Replaced filesystem operation with io_handler

Reviewed By: arknapit, YanNoun

Differential Revision: D29134054

fbshipit-source-id: d9490810eeaf93bd6cef7209059b8f39ccd6b483

mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM,mapillary/OpenSfM