Reorganize header files (Ticket #97)

In addition on some places the DefaultMap<G, K, V> is replaced with
ItemSetTraits<G, K>::template Map<V>::Type, to decrease the dependencies
of different tools. It is obviously better solution.

 include_directories (${LEMON_SOURCE_DIR})

 add_library (lemon arg_parser.cc base.cc color.cc random.cc)