Repair alarms part 1

We need to make sure all the collections are enabled, otherwise we'll
never get to see any item in the calendar. I wonder if that ever worked,
to me it looks like korgac could have been broken since the introduction
of the KCheckableProxyModel.

It is a rather crude implementation as we blindly enable all the
available collections here. We might want to improve that later by
enabling only a subset based on some settings (either specific to korgac
or in sync with korganizer). That's to open up that path that I didn't
simply use setCollectionFilteringEnabled(false) on purpose.