Dependency License checking

[Andy Seaborne]

This maybe helpful in preparing the code for release: it was mentioned 
on the Rya list:

mvn license:aggregate-add-third-party
egrep -iv "BSD|ASF|MIT|CDDL|EPL|Apache|Eclipse|Public Domain" \
           target/generated-sources/license/THIRD-PARTY.txt

Not perfect but greatly reduces the workload.

        Andy