Exception hierarchy sketch.
Exception safe exception classes.
1 hier: hierarchygraph.h hierarchygraph_test.cc
2 g++ -Wall -W -I../.. -I../klao -I../../lemon hierarchygraph_test.cc -o test
4 edge: edgepathgraph_test.cc edgepathgraph.h
5 g++ -Wall -W -I../.. -I../klao -I../../lemon edgepathgraph_test.cc -o test