Added stack buckets and bucket filler classes.
Corrected name of tree knot accessor since it is not an implementation object.
Slight changes to tree class.
Changed edge to be an accessor object.
Created implementation classes for graph.
Created accessor for graph nodes.
Moved graph traversal to own module.
Converted graph class to accessor class and removed graph traversal from module.
Adapted graph builder to separation of accessors and implementation.
Adapted spanning tree iterator to separation of implemention and accessors for graph classes.
Fixed spanning tree tests.
Fixed consistency of constructor arguments and fields.
Changed graph builder result to be graph implementation.
Added free function to get spanning trees for graph.
Added shadow patches to model implementation.
Converted patch class to accessor class and added apropriate iterators.
Moved old patch class to obsoleted module.
Created model accessor class.
Improved model builder to use bucket filler.
Made generate facetree return tree accessor class.