Add GLAD `match_condition` to match rules

[fjuniorr]

In GLAD Flow Mapping format there is a column MatchCondition defined as:

Single character. =, >,<,~. Meaning 'equal to','a superset of', 'a subset of', 'a proxy for'. Assumes = if not present

We currently don't have this definition in each match rule.

[cmutel]

Strong negative reaction to including these symbols verbatim. I have used verbs from a common semantic ontology for these concepts in the past, but don't find them now. Given our matching strategies I would put this as nice to have for now.