Moved Rating module introduction to Rating index

Rating module introduction has been moved to respective index.
Some rewriting has been made in order to achieve a clearer and
more concise user documentation.

Change-Id: Ied923a0e6eb5259a5910e104a46a64c16ecbfdd3

doc/source/user/rating/index.rst

@@ -2,9 +2,87 @@
 Rating
 ======
 
+CloudKitty is shipped with three rating modules:
+
+* ``noop``: Rating module for testing purpose (enabled only).
+
+* ``hashmap``: Default rating module corresponding to usual CloudKitty
+  use cases (disabled by default).
+
+* ``pyscripts``: Custom rating module allowing you to add your
+  own python scripts (disabled by default).
+
+You can enable or disable each module independently
+and prioritize one over another at will.
+
+* ``Enabled`` state is represented by a boolean value (``True`` or ``False``).
+* ``Priority`` is represented by an integer value.
+
+.. note::
+
+   The module with the biggest priority value will process data first
+   (descending order).
+
+List available modules
+======================
+
+List available rating modules:
+
+.. code:: console
+
+    $ cloudkitty module list
+    +-----------+---------+----------+
+    | Module    | Enabled | Priority |
+    +-----------+---------+----------+
+    | hashmap   | False   | 1        |
+    | noop      | True    | 1        |
+    | pyscripts | False   | 1        |
+    +-----------+---------+----------+
+
+Enable or disable module
+========================
+
+Enable the hashmap rating module:
+
+.. code:: console
+
+    $ cloudkitty module enable hashmap
+    +---------+---------+----------+
+    | Module  | Enabled | Priority |
+    +---------+---------+----------+
+    | hashmap | True    | 1        |
+    +---------+---------+----------+
+
+Disable the pyscripts rating module:
+
+.. code:: console
+
+    $ cloudkitty module disable pyscripts
+    +-----------+---------+----------+
+    | Module    | Enabled | Priority |
+    +-----------+---------+----------+
+    | pyscripts | False   | 1        |
+    +-----------+---------+----------+
+
+Set priority
+============
+
+Set the hashmap rating module priority to 100:
+
+.. code:: console
+
+    $ cloudkitty module set priority hashmap 100
+    +---------+---------+----------+
+    | Module  | Enabled | Priority |
+    +---------+---------+----------+
+    | hashmap | True    | 100      |
+    +---------+---------+----------+
+
+More details
+============
 .. toctree::
+   :maxdepth: 2
    :glob:
 
-   introduction.rst
    hashmap.rst
    pyscripts.rst

doc/source/user/rating/introduction.rst

@@ -1,66 +0,0 @@
-==========================
-Rating module introduction
-==========================
-
-There are three rating modules in Cloudkitty now, including the ``noop``,
-``hashmap`` and ``pyscripts``. Only the noop rating module is just for
-testing. All modules can be enabled and disabled dynamically. Cloudkitty
-allows to run several rating modules simultaneously, and the user or
-operator can set the priority for a module. The order in which the modules
-process the data depends on their priority. The module with the highest
-priority comes first.
-
-List current modules
-====================
-
-List current rating modules:
-
-.. code:: raw
-
-    $ cloudkitty module list
-    +-----------+---------+----------+
-    | Module    | Enabled | Priority |
-    +-----------+---------+----------+
-    | hashmap   | False   | 1        |
-    | noop      | True    | 1        |
-    | pyscripts | True    | 1        |
-    +-----------+---------+----------+
-
-Enable or disable module
-========================
-
-Enable the hashmap rating module:
-
-.. code:: raw
-
-    $ cloudkitty module enable hashmap
-    +---------+---------+----------+
-    | Module  | Enabled | Priority |
-    +---------+---------+----------+
-    | hashmap | True    | 1        |
-    +---------+---------+----------+
-
-Disable the pyscripts rating module:
-
-.. code:: raw
-
-    $ cloudkitty module disable pyscripts
-    +-----------+---------+----------+
-    | Module    | Enabled | Priority |
-    +-----------+---------+----------+
-    | pyscripts | False   | 1        |
-    +-----------+---------+----------+
-
-Set priority
-============
-
-Set the hashmap rating module priority to 100:
-
-.. code:: raw
-
-    $ cloudkitty module set priority hashmap 100
-    +---------+---------+----------+
-    | Module  | Enabled | Priority |
-    +---------+---------+----------+
-    | hashmap | True    | 100      |
-    +---------+---------+----------+