doc/*: Document Python bindings

src/python/basic_graph.cpp src/python/basic_graph.hpp:
  - Add ability to record the names of vertices input via the adjacency list
    reader.

example/python/breadth_first_search.py: Building a better example


[SVN r28350]

libs/graph

@@ -1 +1 @@
-Subproject commit efc05efebd028201d4bd8c1e0bf237dd087de925
+Subproject commit 34bc3a8786acabc3f04b61bd765c11024575cd61