Allow to add separator

Until now, all the menu entries were shown in a continuous list, one
after another. This patch allows to add separators between entries.

src/devedeng/separator.py

@@ -0,0 +1,48 @@
+# Copyright 2019 (C) Raster Software Vigo (Sergio Costas)
+#
+# This file is part of DeVeDe-NG
+#
+# DeVeDe-NG is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# DeVeDe-NG is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>
+
+from gi.repository import Gtk, GObject
+import os
+
+import devedeng.configuration_data
+import devedeng.interface_manager
+
+class separator(devedeng.interface_manager.interface_manager):
+
+    __gsignals__ = {'name_changed': (GObject.SIGNAL_RUN_FIRST, None, (str,)), 'in_menu_changed': (
+        GObject.SIGNAL_RUN_FIRST, None, (bool,))}
+
+    def __init__(self):
+        self.element_type = "separator"
+        devedeng.interface_manager.interface_manager.__init__(self)
+        self.add_toggle("show_in_menu", True)
+        self.add_text("separator_name", _("Separator"))
+
+    def set_name(self, new_name):
+        self.separator_name = new_name
+        self.emit('name_changed', self.separator_name)
+
+    def delete_element(self):
+        return
+
+    def store_element(self):
+        data = self.serialize()
+        data["element_type"] = "separator"
+        return data
+
+    def restore_element(self, data):
+        self.unserialize(data)