edit-dialog: add 'Repeat' options for simple recurrences

Currently, creating recurring events is not supported
in gnome-calendar.

This patch adds a Repeat combobox with a list of
simple recurrences such as:

 * Monday - Friday events
 * Daily events
 * Weekly events
 * Monthly events
 * Yearly events

and also a list of recurrence-duration-types such as:

 * If an event should repeat forever
 * A date until which the event should repeat
 * Number of times an event should repeat

It enables the user to create simple recurring events and
even modify the recurrence-property of an already
recurring event.

https://bugzilla.gnome.org/show_bug.cgi?id=782755

src/gcal-edit-dialog.h

@@ -55,6 +55,8 @@ GDateTime*           gcal_edit_dialog_get_date_end            (GcalEditDialog *d
 
 GDateTime*           gcal_edit_dialog_get_date_start          (GcalEditDialog *dialog);
 
+gboolean             gcal_edit_dialog_get_recurrence_changed   (GcalEditDialog *self);
+
 G_END_DECLS
 
 #endif /* __GCAL_EDIT_DIALOG_H__ */