[MIG] web_notify: Migration to 12.0

Add self-test buttons in demo environment,
Updated readme to show how to test it.
Add buttons to users form
Do not rely on SUPERUSER_ID and avoid getattr usage

web_notify/readme/CONTRIBUTORS.rst

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+* Laurent Mignon <laurent.mignon@acsone.eu>
+* Serpent Consulting Services Pvt. Ltd.<jay.vora@serpentcs.com>
+* Aitor Bouzas <aitor.bouzas@adaptivecity.com>

web_notify/readme/DESCRIPTION.rst

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+Send instant notification messages to the user in live.
+
+This technical module allows you to send instant notification messages from the server to the user in live. 
+Two kinds of notification are supported.
+
+* Warning: Displayed in a red flying popup div
+* Information: Displayed in a light yellow flying popup div

web_notify/readme/INSTALL.rst

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+This module is based on the Instant Messaging Bus. To work properly, the server must be launched in gevent mode.

web_notify/readme/USAGE.rst

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+
+To send a notification to the user you just need to call one of the new methods defined on res.users:
+
+.. code-block:: python
+  
+   self.env.user.notify_info(message='My information message')
+
+or 
+
+.. code-block:: python
+  
+   self.env.user.notify_warning(message='My marning message')
+
+.. figure:: static/description/notifications_screenshot.png
+   :scale: 80 %
+   :alt: Sample notifications
+
+You can test the behaviour of the notifications by installing this module in a demo database.
+   Click in your user logo in the top right corner of the screen then click "Preferences".
+
+.. figure:: static/description/test_notifications_demo.png
+   :scale: 80 %
+   :alt: Sample notifications