Core: replace getCompositeValue() (#339).

getCompositeValue() is replaced by 2 different methods.

BREAKING CHANGES

DeepaMehtaObject:
    CompositeValue getCompositeValue() -> ChildTopics getChildTopics()
    # changed semantics!
    # ChildTopics is attached to the DB!

DeepaMehtaObjectModel:
    CompositeValue getCompositeValue() -> ChildTopicsModel getChildTopicsModel()
    # just a renaming

Note: in 4.0.14 both getCompositeValue() methods returned a model, the same model. Now they have different semantics:
    - getChildTopics() returns an application object that is attached to the DB.
    - getChildTopicsModel() returns just a model, like before.
So, also the child topics (formerly: "composite values") follow the very pattern that is applied to all the other core objects (topic, association, ...).

When your plugin makes use of getCompositeValue() it must be adapted. 2 cases:
    1) dmObject.getCompositeValue() -> dmObject.getModel().getChildTopicsModel()
    2) dmModel.getCompositeValue()  -> dmModel.getChildTopicsModel()
With these 2 transformations your 4.0.14 code will have exactly the same semantics as before.

On the other hand, to take benefit from the fact child topics are now attached to the DB, you would write
    dmObject.getChildTopics()...
However, for the moment the ChildTopics object is not yet fully functional.

Generally: in the near future, to perform update operations on child topics you will use the (attached) ChildTopics object. This is convenient (and in accordance with the rest of the DM core API) as DM keeps the model (memory) and DB in-sync automatically. Only in rare occasions you might want to manipulate the model directly while leaving the DB untouched (resp. update it later).

One more note: conceptually both expressions have exactly the same semantics:
    1) dmObject.getModel().getChildTopicsModel()
    2) dmObject.getChildTopics().getModel()
However, there is a bug in DM that prevents expression 2) from working. So, for the moment you must use expression 1).

This branch ("attach-comp-value") is fully functional.
All plugins of the standard distro are already adapted.

Please try out this branch and adapt your plugins soon.

See ticket 339.