There's already "QML modules", which are contained within "Qt modules".
C++ APIs are siblings of QML APIs, but aren't encapsulated in a
module-like containers. So, let's not call them modules.

This completes https://codereview.qt-project.org/#change,54430



Change-Id: I26b86555749f3b0d03082427f6365458fb3735f7
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>