replace  both "Class" and "Interface" classes  with "GenericContainer" class.
finish the implementation of class "DiagramComponentFactory","Diagram".
update "keys" class.
implements update and toJSON in both "oval" and "actor".
implements writeExternal function in "Diagram" class, also add new properity diagram type.
create new class "DiagramType" represent types of diagrams.
remove "UseCase" class duplicate in the code.