Xtu Code

Added a first shot at an association schema.

Added inheritance to class definitions

Replaced NonEmptyStringType with NMToken where meaningfull.

Set default state transition rule to be ILLEGAL

Added a missed type checking for state signatures

Added type integrity checks for all parameters and returns

Restructured and cleaned up the inlclusion of data types in a model.

Got type name checking working. I.e. a check that type names used for PIM variables actually exist.

Minor cleanups

Added identifier to class' member variables