Print the number of nodes and edges.

* include/qdft/manager.hh,
* include/qdft/manager.hxx: Provide get_graph_size method.

* include/qdft/qdft.hh,
* include/qdft/qdft.hxx: Provide get_graphs_size method.

* src/test_lib.cc: Print total number of nodes and edges in addition to
  memory footprint.
Update Doxyfile for doxygen 1.8.
Improve project configuration.

* configure.ac: Add option disable-documentation and define HAVE_TCL_H
  if tcl8.5/.tcl.h is found.
* include/Makefile.am: Compile qdft_wrap.cxx iff. HAVE_TCL_H is defined.