minimal pom

Create a pom file for the plugin
update ignores
Minor GUI change

shorten the button string, to improve readability
Merge commit '45bee42a99e3fff30119abc47c5a268556d1be7b' into additional-OBO-properties
comment and cardinalty

* introduce cardinality constraint (max)
* make xref usage configurable
* add comment
Merge branch 'additional-OBO-properties'