Switching constructor and node implementations from vectors to lists.
Caching length because of O(n) cost with immutable list.
Fallback to default generated hashCode and equals methods in Tuple.

Further
* fixing a regression due to a partial commit in ValueFactory.
* adding @tailrec annotation to recurse function in Relation, to assure optimization.
Adding constructor from open arguments list.
Sketching outline of StringValue class.
Adding custom value and type classes (experimental).

Are not used currently.
Adding test classes, to parametrize tests by this projects ValueFactory.
Changing semantics of isSubMap due to changes in pdb.values.
Classpath change due to test folder.
Adopting previous pdb.values changes + new ListRelation type.

* Further, removal of case class keyword for writer classes.
* Introduction of SetOrRel and ListOrRel abstraction factories.
* ...
Partially cleaned up ValueFactory.

Done for Set and Relation types.
Remove code that is covered by SetOrRel and ListOrRel.
Cleanup of List[Relation]Writer.
Switching to Scala 2.10.0.

Removing case classes from non-leaf nodes in class hierarchy (List, Node, Set).
Adding companion objects.
Adding hashCode and equals (= same as in Node).
Updating copyright notice.

Plus small fixes.