features: added experimental root feature for surf/akaze
features: added experimental root feature for surf/akaze

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