Fix entity mapper's input to mirror the represenation's input

In order to get consistent ordering for cell selection (and, therefore,
point picking), we must construct a multiblock dataset that has the
same hierarchical structure as the input data set. We don't want to
have component or instance rendering from our entity mapper, though, so
we simply leave those blocks out of our new dataset.

This fix will likely need to be revisited once we get to prototype
selection.
Status Job ID Name Coverage
  External
passed cdash

passed ghostflow-branch-check-master

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

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

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

failed 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

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

failed smtk@master-talosiv-osx-shared-release+examples+matplotlib

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

failed smtk@master-tatooine-osx-shared-release+examples+matplotlib+private

passed cdash

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

00:01:21

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

00:03:21

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

00:00:05

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

00:03:24

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

00:03:20

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

00:02:25

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

00:01:22

failed smtk@master-talosiv-osx-shared-release+examples+matplotlib

00:06:54

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

00:01:52

failed smtk@master-tatooine-osx-shared-release+examples+matplotlib+private

00:02:20