fixed the UWSpotForm unit tests to work with the new validation provided by uiuc

fixes SPOT-1023
adds a uw unit test to make sure that extended info exists on a POST

fixes SPOT-1022

initially we thought this could be done with just a spot.save(), but
the extendedinfo form validation only happens with spotform after
restful calls and is not triggered on a simple spot.save()

also fixes a bug where sometimes the json_error method in the rest
dispatch would return an empty string as the error message
turns has_labstats into a uw validated extended info field

fixes SPOT-1046