dateMenu: Try to use the default calendar application

Commit 14ceb105 changed the "Open Calendar" item to open the
"recommended" calendar application rather than the default one to
avoid problems with MIME subclassing (namely falling back to the
default text editor when no calendar app is installed).
With this change however, the application launched does no longer
necessarily match the one configured in Settings, which is unexpected.
To avoid both problems, use the default calendar application again,
but only if it is in the list of recommended applications.

https://bugzilla.gnome.org/show_bug.cgi?id=722333