Added support for global label file when loading graphs.

Change-Id: I6c62aa5e06ce16631f89a2fb1f78593aed7f6a7e
ENH: support for a global label file.

Change-Id: I6b0821e0ece99202195c1918188a77a77cf8773c
Merge topic 'rk-MoreRenameFixes'

8df759a ENH: support for a global label file.
2f9068f Added support for global label file when loading graphs.