qdoc: Allow documenting a C++ class as a QML type.

qdoc: Allow documenting a C++ class as a QML type.

Now qdoc can handle the case where a C++ class is
documented as a QML type of the same name, or as
both a C++ class and a QML type of the same name.

And collisions pages are created for both the HTML
and the DITA XML output. A collision page is created
when two items have the same name. The collision
pages will be augmented later to include the list
of pages where ambiguous links to one of the items
listed on the collision page are actually located,
so the writer can go back to those links and add
the appropriate qualifier.

Change-Id: I5a9632b2d2209e0784392047056bed8962005624
Reviewed-by: Martin Smith <martin.smith@nokia.com>
Reviewed-by: Casper van Donderen <casper.vandonderen@nokia.com>