Improve EMF constructor generator generated JavaDoc

We have an EMF constructor generator that is used to generate convenient constructors from Ecores. We generate e.g. CifContructors using it. The JavaDoc of the generate constructor classes could be improved:

• According to the JavaDoc, parameters can be null even for mandatory features. This allows constructing partial models, not setting some features when constructing them, and later setting them using setters. The JavaDoc could be more clear here, distinguishing allowing it temporarily to construct partial models to be completed later vs the requirements for complete models. It would be good to indicate the multiplicity of the features as well.
• For the overloads without parameters, which also create partial objects, some JavaDoc would be good to indicate that it is partial.