TEX11 — Update section 10.5 "DDS PSM" to take advantage of new ISO IDL4 features

The DDS PSM was defined before IDL 4 was introduced and therefore could not take advantage of features that are now part of IDL 4 but were not in IDL 3.x.
IDL4.2 is now well stablished and ISO specification as well . And moreover both OpenSource and Commercial DDS vendors support it. Therefore it makes sense to update the "DDS PSM" to use these features. This will result in more natural language mappings as well as more efficient serialization.

The recommended changes are:
In 10.5 DDS PSM perform the following edits:

Replace the bullet:

• Optional attributes are mapped to a union type with a single member present when the exists case attribute is true.
  With:
• Optional attributes are mapped to IDL attributes of the same type annotated with the "@optional" annotation.

Replace the bullet:

• Specialization / Generalization PIM relationships are mapped to IDL unions. Additional data classes are introduced for generalization classes that have attributes.
  With:
• Specialization / Generalization PIM relationships are mapped to IDL structure inheritance. All the structures that participate in a Specialization / Generalization relationship are annotated with the "@appendable" annotation.