Addressing the problem of subgraphs (not) working with bundled properties.

Added some comments, documentation, and a new test.


[SVN r50533]

libs/graph

@@ -1 +1 @@
-Subproject commit 3fbb14a5cf24059b9429edbec4f9046e5c4489c2
+Subproject commit af7369b6b03c39385d31d64049422259a038c26e