SYSML2_ — Replace Generic mapping classes by Initializers

The coexistence of both the "GenericTo*_Mapping" classes and the Initializer classes generates a significant number of redundancies in the model, and make it harder to understand and to maintain.

More specifically it makes the management of redefinitions much more complex with a very negative impact on the clarity of the specification.

In order to fix that, all the GenericTo*_Mapping classes shall be removed and replaced par their Initializer class equivalent in an appropriate way.