fix(notifications) the notification plugin miss the plugin installation

Signed-off-by: Benoit Mortier <benoit.mortier@fusiondirectory.org>

source/fusiondirectory/plugins/notifications/configuration.rst

+Configuration
+=============
+
+The list of attributes **must be** configured via the **FusionDirectory configuration menu** under the **Notifications** tab before use.

source/fusiondirectory/plugins/notifications/description.rst

+Description
+===========
+
+This plugin is used in the manage possibility of getting notified of attributes or supann ressources change on a set of users
+
+
+
+

source/fusiondirectory/plugins/notifications/index.rst

@@ -5,4 +5,7 @@ Notifications
 .. toctree::
    :maxdepth: 2
 
-   notificationsTask.rst
+   description
+   installation
+   configuration
+   notificationsTask

source/fusiondirectory/plugins/notifications/installation.rst

+Installation
+============
+
+Install packages
+----------------
+
+Debian
+^^^^^^
+
+.. code-block:: bash
+
+   apt-get install fusiondirectory-plugin-notifications
+   apt-get install fusiondirectory-plugin-notifications-schema
+
+Install schemas
+---------------
+
+Debian
+^^^^^^
+
+.. code-block:: bash
+
+   fusiondirectory-schema-manager --insert-schema /etc/ldap/schema/fusiondirectory/notifications-fd.schema
+   fusiondirectory-schema-manager --insert-schema /etc/ldap/schema/fusiondirectory/notifications-fd-conf.schema
+
+Register the plugin
+-------------------
+
+.. code-block:: bash
+ 
+   fusiondirectory-plugins-manager --register-plugin /etc/fusiondirectory/yaml/notifications/description.yaml