Initial commit of the object mother #498

Add a simple king and queen classes which implement the behaviour of the
royalty interface. Also wrote the object mother of royalty objects which
is final so you can just call the static methods in it to create objects
with a specific state to use them fast in tests. The tests are already
created for testing the behaviour and the type of the objects which are
created by the object mother.
I also created the UML diagrams via object aid and updated the readme.