Better handling of multi-typing in SHACL generation algorithm

[tfrancart]

We have some intelligence in the property shapes range calculation, to reduce the list of the classes we find: in AssignClassesVisitor, using ClassCacheProvider.

Now we should do the same to reduce the number of classes that are analyzed at the beginning of the script.

For each type T in all found types:

• if T co-occurs with other types, then:
  • if T is a superset of all other types (it always occur with other types, and no instances of another occur without it), then:
    • if it is a union of all other types (no instance of T occur without a class in the other types list), then : ignore all other types (or add them as empty shapes, with a rdfs:subClassOf to T)