First pass working
Generalized tabs, first cut at interactive segmentation.
Expose segment/fill to GUI.  No saving or contour conversion yet.
Merge branch 'tabs'

Better looking annotation widget in tabs.  Plus the start of a new segmentation tool.

* tabs:
  Expose segment/fill to GUI.  No saving or contour conversion yet.
  Generalized tabs, first cut at interactive segmentation.
  First pass working