+ Add property and property-storage classes.
+ Eliminate duplicate floating-point storage in smtk::model.
+ Eliminate `smtk/model/FloatData.h`.
  These types have moved to `smtk/resource/PropertyType.h`.
+ Eliminate m_floatData in smtk::model::Resource and methods
  that provided access.
  The new methods for accessing property are available on
  a per-entity basis in smtk::model::EntityRef.
+ Move SetProperty operation from model to operation
  directory/namespace.