Various bug fixes and code improvements in adaptors.h (#67)

- Fix UndirectorBase::nodeNum().
- Fix UndirectorBase::findEdge().
- Fix OrienterBase::addArc().
- Fix OrienterBase::findArc().
- Improve SplitNodesBase::findArc().
- Add missing notifier() function in UndirectorBase.
- Add missing typedefs for maps (conform to the ReferenceMap concept).
- Add some useful typedefs for graph adaptors.

 @nodes

 label

 0

 1

 2

 3

 4

 5

 6

 7

 8

 9

 @arcs

 		label	capacity

 0	1	0	20

 0	2	1	0

 1	1	2	3

 1	2	3	8

 1	3	4	8

 2	5	5	5

 3	2	6	5

 3	5	7	5

 3	6	8	5

 4	3	9	3

 5	7	10	3

 5	6	11	10

 5	8	12	10

 6	8	13	8

 8	9	14	20

 8	1	15	5

 9	5	16	5

 @attributes

 source 1

 target 8