GenericThread used to accept an optional "parent" argument, defaulting to nullptr.
This was odd, because the moveToThread() in GenericThread::initialize() would
become a no-op if the instance ever inits QObject(someNonNullParentQObject).
(The only clue would be a log message "QObject::moveToThread: Cannot move objects with a parent",
and things would end up in the same thread that created the instance.)
As it turns out, all the subclasses of GenericThread do not init
GenericThread(parent), so things worked as expected.
