Merge branch 'develop'
Added support for mereologies

Fixes #16. It simply adds two new relations, the code in
RelationCheck.java was already there.
Minor fix, rule priority

We get only one code for each pair or fields although several
possibilities exist. This is similar to a t-conorm so we try to return
the maximum or the best match possible between two concepts.
Merging mereologies into develop

It was simple, in retrospective.
Expression handling second version

Warning: not the most tested code ever. Tests pending. WIP.