ENH: Adding observers to AssociationWidget and ModelEntityAttributeView

- Also fixed Import Issue
- Added reference to operation manager in Attribute Panel
- Resource Manager now tells observers a resource has been removed after it has been removed from the manager's set of resources and the resource's manager is cleared.
- Attribute Association operator now returns the attribute resource being modified in its result
18 jobs for addingOpObserversToViews
Status Job ID Name Coverage
  External
passed cdash

passed ghostflow-branch-check-master

pending smtk@master-junction-osx-shared-release+remus
passed smtk@master-kerbin-windows-shared-release+examples+remus

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+python3+remus+vtk

passed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus+vtk

passed smtk@master-norkit-osx-shared-release+examples+matplotlib

passed smtk@master-praxis-windows-shared-release

pending smtk@master-talosiv-osx-shared-release+examples+matplotlib
passed smtk@master-tatooine-osx-shared-release+examples+matplotlib

passed smtk@master-kerbin-windows-shared-release+examples+remus

00:02:54

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+python3+remus+vtk

00:01:39

passed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus

00:01:42

failed smtk@master-moho-linux-shared-relwithdebinfo+examples+remus+vtk

00:01:32

passed smtk@master-norkit-osx-shared-release+examples+matplotlib

00:03:46

passed smtk@master-praxis-windows-shared-release

00:03:11

passed smtk@master-tatooine-osx-shared-release+examples+matplotlib

00:02:11