Add missing accelerator for <Alt>+Down as it was
mentioned in shortcuts dialog but not implemented.
Fixes#492
Signed-off-by: Rajat Jain <rajatjain.ix@gmail.com>
Using dialog responses to communicate intent to GcalWindow was always
a hack, and as the code is cleaned, it's getting increasingly annoying.
Replace this with a proper 'remove-event' signal ('delete-event' would
conflict with the equally named GTK signal), remove the custom response
types, and cleanup the code.
Georges Basile Stavracas Neto