QVT — Rules for infering an extent

The rules for inferring an extent from the type are not explained or referenced.
Note: This issue is related to issue: 9388

In relation with resolution 9388, replace the text describing the "modelParameter" role:

The extent of the mapping parameter. Should be explicitly provided
when there is an ambiguity on the extent that will own a potential
created element corresponding to this parameter.

By:

"""
The extent of the mapping parameter. If not provided the extent is inferred by inspecting the model types of the transformation. See the inference rules below.
"""

In addition, after the description of the metaclass properties, add the following paragraph:
"""
Extent inference rule for mapping parameters:
If the mapping parameter direction is "in", inspect the input model types of the transformation to find the one that contains the type of the parameter. A model type "contains" a type if the type is directly or indirectly contained by the package defining the model type.
If the model parameter direction is "inout" or "out", inspect the inout or output model types of the transformation to find the one that contains the type of the parameter.
In both cases there should be a unique model type found.
"""