Check for 'package://' syntax and warn once
Check for 'package://' syntax and warn once

URDFRigidBodyManipulator presently does not support the 'package://' syntax for
specifying mesh filenames. Rather than spam the user with a warning for each
mesh file, we now warn once per urdf that uses that syntax.

billhoffman/drake,hanssusilo/drake,scottviteri/drake,crogers3/drake,manuelli/drake,scottviteri/drake,billhoffman/drake,edowson/drake,astrorog/drake,sheim/drake,sheim/drake,edowson/drake,edowson/drake,hanssusilo/drake,astrorog/drake,astrorog/drake,crogers3/drake,manuelli/drake,psiorx/drake,tkoolen/drake,scottviteri/drake,sheim/drake,thientu/drake,manuelli/drake,tkoolen/drake,manuelli/drake,tkoolen/drake,sheim/drake,tkoolen/drake,crogers3/drake,edowson/drake,edowson/drake,thientu/drake,billhoffman/drake,billhoffman/drake,thientu/drake,astrorog/drake,billhoffman/drake,hanssusilo/drake,edowson/drake,billhoffman/drake,psiorx/drake,billhoffman/drake,manuelli/drake,hanssusilo/drake,crogers3/drake,crogers3/drake,tkoolen/drake,sheim/drake,thientu/drake,astrorog/drake,psiorx/drake,thientu/drake,thientu/drake,astrorog/drake,hanssusilo/drake,billhoffman/drake,hanssusilo/drake,hanssusilo/drake,thientu/drake,psiorx/drake,scottviteri/drake,psiorx/drake,tkoolen/drake,crogers3/drake,sheim/drake,edowson/drake,psiorx/drake,scottviteri/drake,crogers3/drake,manuelli/drake,manuelli/drake,scottviteri/drake,psiorx/drake,crogers3/drake,edowson/drake,hanssusilo/drake,sheim/drake,psiorx/drake,tkoolen/drake,sheim/drake,scottviteri/drake,astrorog/drake