NUTCH-2621 Generate report of third-party licenses

[sebastian-nagel]

• add ant target ant report-licenses (for core and plugins) which generates tabular reports of dependency licenses

The created table is comparable to those created by the Maven license plugin

• it also shows dual licenses (important if one of the alternatives is compatible with the Apache license)
• must be called separately for core and each plugin, e.g.

# Nutch core
ant report-licenses
more build/org.apache.nutch-nutch-default-3rd-party-licenses.tsv

# plugin any23
cd src/plugin/any23
ant report-licenses
more ../../../build/any23/org.apache.nutch-any23-default-3rd-party-licenses.tsv

[lewismc]

+1