Connection list with add folder button and removed naming bug

The creation of folders was not clear and a bug could rename wrong
elements, which the user does not select.
Now connections and folders are handled in separat ways and the user can
add a new folder by pressing a button.

ui_dev/ressources.qrc

@@ -9,6 +9,7 @@
     <file>ico/file-python.ico</file>
   </qresource>
   <qresource prefix="action">
+    <file>ico/edit-delete-6.ico</file>
     <file>ico/applications-utilities.ico</file>
     <file>ico/edit-find.ico</file>
     <file>ico/process-stop.ico</file>