* attribute::Attribute
 * Removed functionality to maintain model::resource's attribute association backstore (no longer needed)
 * Added a protected method forceDisassociate that will bypass disassociation checks.  This is used by the attribute::Resource when disassociating all attributes from an object.
 * Added association checks to the associate method.
* attribute::Resource
 * Added hasAttributes method to check to see if an object has attributes associated to it
 * Added disassociateAllAttributes method to remove all attribute associations from an object
* model::Entity
 * Removed functionality to maintain model::resource's attribute association backstore (no longer needed)
* model::EntityRef
 * Removed functionality to maintain model::resource's attribute association backstore (no longer needed) and replaced it with link-based functionality
 * Added hasAttributes(smtk::attribute::ConstResourcePtr attRes) const
 * Added disassociation methods that don't take in the reverse bool parameter.  The original API which does take in the reverse parameter is marked for deprication (via comment) and calls the new API
* Added Pybind11 Registrar methods for smtk::model