This commit contains many changes from Alvaro Sanchez and me to address:
+ Color-by-entity and -by-volume mode for the model representation.
  In cases where the begin() entity is invalid, volumeOfEntity() would
  return an entity not flagged as being a volume.

  In order to get access to an EntityRef's color property, pqRepresentation
  provides a smtk::model::ManagerPtr to the vtkSMTKModelRepresentation object.

  The appropriate EntityRef is queried from model::ManagerPtr (Resource)
  depending on the active coloring mode; color-by-entity uses direclty its
  entity color and color-by-volume uses the color of the 0th volume bounded
  by the entity.
+ Use pqSMTKResource's model::Manager instead of a global instance.
+ Representation subtypes (points, wireframe, surface, surface with edges)
  for the model representation.
+ Line color for the model representation.
+ Representation class location.
  Move the server-side classes to the PV server extension and add
  pqProxy subclasses to the appcomponents extension.
  This is necessary to avoid cyclic dependencies between the representation
  and the resource panel (which will soon display/modify the representation's
  visibility information).
+ Move DescriptivePhrase subclasses (that describe content) into
  a PhraseContent class, instances of which are owned by DescriptivePhrase.
  This separates the hierarchy of subjects from the content of the subject
  so that attributes of the subject can be overridden via the decorator pattern.
  This leaves phrase lists with improper descriptions at the moment
  since the common/union flag values are not set properly (among other things).
+ Displaying "eyeball" visibility icon selectively -- only
  when the PhraseContent advertises it as available is it rendered and active.
+ Use the new visitor method of vtkCompositeDataDisplayAttributes to
  fetch per-view block visibility information from mappers and add
  methods to set the per-block visibility, although this is not complete yet.
  This requires us to bump VTK and PV forward, which in turn requires us to
  Fix build issues due to changes in wrapping.
    + Fixes errors: No rule to make target '*Hierarchy'.
    + Manually excludes classes that do not need wrapping.
+ Try to keep `ENTITYID` out of SMTK except for the `vtkModelMultiBlockSource`.
+ Attach UUID to both the multiblock metadata and the actual `vtkDataObject`
  instance. The latter is preferrable in almost every instance since it is
  then possible for methods passed only a data object to get its UUID.
  This is necessary for the PV representation's visibility modification
  queries to work properly since, when iterating over visibility entries in
  vtkCompositeDataDisplayAttribute, only the block is available, not its metadata.
+ Add missing parts to representation xml: property to enable/disable
  multi-block inspector coloring.
+ Create and make representations visible by default in new views.
  pqApplyBehavior makes the model visible on the initial view. Additional
  views need to create and make their representations visible, this is done
  through pqSMTKBehavior.
+ Fix some crashes by holding a weak ref to the selection.

Co-authored-by: Alvaro Sanchez <alvaro.sanchez@kitware.com>