A tree structurization of known tags

For various other features, a tree (or rather oriented graph) structure of predefined core tags would be handy, such like:

jboss-eap-5
   contains: java-ee-5
   contains: java-ee
   contains: jms
   contains: hibernate-3
java-ee
   contains: jms
hibernate-3
   contains: jpa-2
...

One feature that could benefit from such known relations is the Lift & Shift report, using whitelisted tags. These would need to include what's inside of them.

Another feature that needs this is the summarization and charts in reports - we shouldn't put each individual tag into the chart, rather group them into groups, like e.g. PaasLane does.

This feature would need to be extensible, i.e. defined in multiple files, brought in by various addons/rulesets.