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/views/gcal-year-view.c

@@ -1398,7 +1398,7 @@ navigator_drag_motion_cb (GcalYearView   *self,
           self->selected_data->dnd_day = day;
           self->selected_data->dnd_month = month;
 
-          gdk_drag_status (context, GDK_ACTION_COPY, time);
+          gdk_drag_status (context, GDK_ACTION_MOVE, time);
 
           retval = TRUE;
         }
@@ -1955,7 +1955,7 @@ gcal_year_view_init (GcalYearView *self)
                      0,
                      NULL,
                      0,
-                     GDK_ACTION_COPY);
+                     GDK_ACTION_MOVE);
 }
 
 static void