VertexProgram.Builder should have a default create() method with no Graph

The VertexProgram.Builder interface has a create(Graph) method, however, the Graph is not always needed. This is illustrated by The GraphComputerTest class with VertexProgramQ and VertexProgramR that both implement create() methods that pass in a null Graph. The Builder should just have this as a default method that will then be inherited by the AbstractVertexProgramBuilder and any subsequent builders that use the abstract class or interface.