We now use icons instead of ASCII art.

+ Implement `PhraseModel::handleCreated()`.
+ Hold expunged model entities rather than UUIDs.
  Change `smtk::model::Resource::deleteEntities()` so that the expunged
  container holds `Entity` shared-pointers rather than UUIDs;
  this keeps the entity records from going out of scope as they are
  removed from the model resource (long enough that the operation result
  can be processed to remove them from the UI).
+ Properly remove phrases of deleted components.
  This also removes overrides that ResourcePhraseModel provided for
  handling operation results; the base class implementation should
  do what is needed without further work by the subclass.
+ Provide a flatter (two-level) resource tree.
+ Documentation for views and phrases.
+ Improve sorting of descriptive phrases
  by comparing smtk::resource::Component subclasses and
  model entity types.
+ Show a valid icon for lists, not the invalid icon.
+ Eliminate some warnings from other parts of SMTK.
+ Make subphrase generator a user preference in the ParaView extensions.

Added new icons for model and attribute resources as well as an icon for attributes.

- Added new ModelEntityAttribute View support (adapted from release branch)
- PersistentObject: added name() method
- atAttribute: now has support for Item::ReferenceType
- Removed old selection manager stuff from qtBaseView
- qtComponentItem: Fixed bug related to extensible items in synopsis method
- Attribute XML Parsers replaced support for model entity items from using reference items to use component items
- Resource:: added a findAs method that can be used to further specialize the results of a query search based on the
container type
- Moved all UI icons into their own directory and removed old qrc file that was redundant
- Fixed potential crash in qtSelectorView when a child view type can not be found