The way we handle singletons in QML, QML insists on allocating the
objects. This leads to a very idiosyncratic way of handling
singletons: The global instance pointer is set in the constructor.
Unify all these by implementing a "SillySingleton" template. All
of the weird singleton-classes can derive from this template and
don't have to bother with reimplementing the instance() function
with all the safety-checks, etc.
This serves firstly as documentation but also improves debugging
as we will now see wanted and unwanted creation and destruction
of these weird singletons.
Signed-off-by: Berthold Stoeger <bstoeger@mail.tuwien.ac.at>
