Graph and UndirGraph concept modifications.

* For incidence iterators ({In,Out,Inc}EdgeIt) there is now baseNode and
runningNode functions in graph interface
* For Edge in undir graphs: Edge(UndirGraph const &, UndirEdge, Node)
constructor. Same for IncEdgeIt
* Edge(UndirEdge, bool) constructor is no more in the public interface. (But we
need it in the developpers interface).

 UnionFind<graph_type, NodeIt> uf( G, G.NodeIt());

 NodeUnionFind<graph_type> uf( G);

 Kell e:

 find visszaadja a nagyfonokot, altalaban kell e a belso tarolobol tudni visszafejteni az ott levo pontot.

 Kell e merge(int, int)

      esetleg merge(Nodeit fonoka, NodeIt fonokb)

 konstruálás map-ből.

 find: visszaad egy egészet

 findAndMerge: visszaad egy boolt