Create entities with more than one type

Entities can now have multiple entity types (e.g. Arnold Schwarzenegger, a Person, Actor, Bodybuilder and Politician). This lets an entity inherit attributes (expected properties and links) from more than one different entity type, greatly enhancing the real-world usability of the graph for modeling data. A more likely business example might be a Company that is also a Customer and/or Supplier, or a Person who is also an Employee.