[blueprint] better heuristic for accessor and global codegraph rank

Test Plan: as usual

Reviewers: akuhn

CC: bryano

Differential Revision: https://phabricator.fb.com/D1096823
* graph_code/graph_code_class_analysis.mli:
[blueprint] support for hierarchy

Test Plan:
the url is now more complicated.
http://pad.dev469.prn1.facebook.com:8080/blueprint?class=BaseFacebookTestCase&hierarchy=down&depth_limit=1

Reviewers: akuhn

CC: bryano

Differential Revision: https://phabricator.fb.com/D1097297
Merge branch 'blueprint'