views: use ACTION_MOVE to display correct cursor

When dragging events around, the cursors show a + as opposed to a
an arrow indicating that the event is being moved. This can confuse
users.

The fix is to tell GTK that the drag being performed is a move.

https://bugzilla.gnome.org/show_bug.cgi?id=774922

src/gcal-event-widget.c

@@ -207,7 +207,7 @@ gcal_event_widget_init (GcalEventWidget *self)
                        GDK_BUTTON1_MASK,
                        NULL,
                        0,
-                       GDK_ACTION_COPY);
+                       GDK_ACTION_MOVE);
 
   gtk_drag_source_add_text_targets (widget);
 }
@@ -843,7 +843,7 @@ gcal_event_widget_set_read_only (GcalEventWidget *event,
                            0,
                            NULL,
                            0,
-                           GDK_ACTION_COPY);
+                           GDK_ACTION_MOVE);
 
       gtk_drag_source_add_text_targets (widget);
     }