[IMP] db_management: rework section for future content

The "database management" section was just a big fourre-tout.

This commit splits a new "Practical Info" section from the
"Applications" section and split the db management page in
3 sub-pages that will be soon extended.

db_management/db_premise.rst

@@ -0,0 +1,38 @@
+:banner: banners/db_premise.jpg
+
+.. _db_premise:
+
+==============================
+On-premise Database management
+==============================
+
+.. _duplicate_premise:
+
+Duplicating a database
+======================
+
+You can duplicate your database by accessing the database manager on your
+server (<odoo-server>/web/database/manager). In this page, you can easily
+duplicate your database (among other things).
+
+.. image:: media/db_manager.gif
+    :align: center
+
+
+When you duplicate a local database, it is **strongly** advised to change
+the duplicated database's uuid (Unniversally Unique Identifier), since this
+uuid is how your database identifies itself with our servers. Having two
+databases with the same uuid could result in invoicing problems or registration
+problems down the line.
+
+.. note:: From July 2016 onward, Odoo 9 now automatically change the uuid of a
+    duplicated database; a manual operation is no longer required.
+
+The database uuid is currently accessible from the menu **Settings > Technical
+> System Parameters**, we advise you to use a 
+`uuid generator <https://www.uuidgenerator.net>`__ or to use the unix command
+``uuidgen`` to generate a new uuid. You can then simply replace it like any
+other record by clicking on it and using the edit button.
+
+.. image:: media/db_uuid.png
+    :align: center