dataset: handle missing config.yaml, allow set image subpath
dataset: handle missing config.yaml, allow set image subpath

NicWayand/OpenSfM,sunbingfengPI/OpenSFM_Test,sunbingfengPI/OpenSFM_Test,BrookRoberts/OpenSfM,onecue/OpenSfM,mapillary/OpenSfM,sunbingfengPI/OpenSFM_Test,NicWayand/OpenSfM,oscarlorentzon/OpenSfM,onecue/OpenSfM,edgarriba/OpenSfM,edgarriba/OpenSfM,mapillary/OpenSfM,BrookRoberts/OpenSfM,NicWayand/OpenSfM,NicWayand/OpenSfM,edgarriba/OpenSfM,sunbingfengPI/OpenSFM_Test,edgarriba/OpenSfM,oscarlorentzon/OpenSfM,oscarlorentzon/OpenSfM,oscarlorentzon/OpenSfM,onecue/OpenSfM,mapillary/OpenSfM,edgarriba/OpenSfM,NicWayand/OpenSfM,onecue/OpenSfM,BrookRoberts/OpenSfM,oscarlorentzon/OpenSfM,BrookRoberts/OpenSfM,mapillary/OpenSfM,BrookRoberts/OpenSfM,mapillary/OpenSfM,onecue/OpenSfM,sunbingfengPI/OpenSFM_Test