Add more relations.
Marks items with no incoming edges as root.
Track satisfies, i.e. inverse of requires.
Add satisfies tests.
Output tree continuation only if there are more nodes to print.
Support Comparable.
Spike finding edge contraction candidates.
Merge branch 'develop' into feature/edge-contraction

Conflicts:
	src/main/java/se/intem/web/taglib/combined/node/ResourceNode.java
	src/main/java/se/intem/web/taglib/combined/node/TreeBuilder.java
Fix bug with printing tree where node requires itself.