Core API wording: rename CompValue pt.1 (#702).

BREAKING CHANGES

Classes/Interfaces:
{{{
CompositeValue -> ChildTopics
    getCompositeValue() -> getChildTopics()
CompositeValueModel -> ChildTopicsModel
    getCompositeValueModel() -> getChildTopicsModel()
}}}

DeepaMehtaObject:
{{{
getCompositeValue() -> getChildTopics()
setCompositeValue() -> setChildTopics()
}}}

DeepaMehtaObjectModel:
{{{
getCompositeValueModel() -> getChildTopicsModel()
setCompositeValue() -> setChildTopicsModel()
}}}

See #702.