added useful error message when invalid ds is provided or no ds is found in vshield_edge

added fix for vshield_dns when a nori string should be converted to an array

removed ds= from vshield_edge

removed surrounding quoutes from edge error msg

changed vnic matching to_s
Merge pull request #31 from sholland/tb/edge_ds_error

added useful error message when invalid ds is provided or no ds is found