Add utilities for allowing views to be GC'ed
Tansform hierarchy widget to be cleanuppable
Make the other parents of hierarchy widget clean it up properly
Restore full auto-update functionality in hierarchy widget
Fix move/copy between different hierarchy widgets
Reduce cyclomatic complexity in geospatial plugin

For some reason this just started failing on travis, not sure
how that's possible.
Merge pull request #575 from girder/garbage-collect-views

Add utilities for allowing views to be GC'ed