#212 Fix var_check handling

[Michael Chisholm]

var_check is not handled correctly in ovaldi, in many places. Many probes handle some var_check values correctly but var_check="none satisfy" incorrectly. There are several probes which for op=equals, ignore var_check completely. This affects partial match reporting too, so partial matching needs to be straightened out. And that will affect the way check_existence works on tests. So all of those things need to be addressed, in order to have a final fix for this issue.