Fix and uniform the usage of Graph and Parent typedefs (#268)

- Rename Graph typedefs to GraphType in the implementation of graph
maps and MapExtender to prevent conflicts (especially using VS).
They are not public.
- Make Parent typedefs private in all classes.
- Replace Digraph with Graph in some places
(fix faulty renamings of the script).
- Use Graph and Digraph typedefs (more) consequently.

 AM_CXXFLAGS = $(WARNINGCXXFLAGS)

 AM_CPPFLAGS = -I$(top_srcdir) -I$(top_builddir)

 LDADD = $(top_builddir)/lemon/libemon.la

 EXTRA_DIST = \

 	CMakeLists.txt \

 	digraph.lgf

 noinst_PROGRAMS = \

 	arg_parser_demo \

 	graph_to_eps_demo \

 	lgf_demo

 arg_parser_demo_SOURCES = arg_parser_demo.cc

 graph_to_eps_demo_SOURCES = graph_to_eps_demo.cc

 lgf_demo_SOURCES = lgf_demo.cc