Issue #2281109: Porting 'Entity is of type (entity_is_of_type)' conditio...

...n to 8.x

See: d.o issue #2281109 - https://drupal.org/node/2281109
This creates an EntityIsOfType condition and an associated test that checks a simulated node's entity type.
We tend to not have camelCased variables. Our class fields are usually camelCased, variables in methods not though. :)