Add screenshot about Fuel CLI warning and edit notes

Currently, User, Operations and Reference Architectures
Guides have poor notes about the changes made
via Fuel CLI and web browser (what takes precedence
and what message appears to warn a user).

This commit adds the required screenshots and
provides some minor changes for the note code.

Change-Id: I739c6db78cf688d5342110d752f8e2631b2be2b6
Closes-Bug: 1374944

pages/operations/5400-puppet-custom-attributes.rst

@@ -17,15 +17,14 @@ Passing custom attributes are useful
 when you have some Puppet manifests that should be run
 but are not supported by Fuel itself.
 
-.. warning::  Be very careful when modifying the configuration files.
+.. warning:: Be very careful when modifying the configuration files.
    A simple typo when editing these files
-   may severely damage your environment.
-
-   When you modify the YAML files,
+   may severely damage your environment. When you modify the YAML files,
    you will receive a warning
    that some attributes were modified from the outside.
    Some features may become inaccessible
-   from the  UI after you do this.
+   from the UI after you do this.
+   Please, read :ref:`Using Fuel CLI <cli_usage>` section carefully.
 
 To do this:
 

pages/reference-architecture/ovs/0200-cli-adjust-network-config.rst

@@ -19,6 +19,7 @@ modify and upload if needed) the environment's 'deployment default' configuratio
 
    Please, make sure you read :ref:`the Fuel CLI documentation <cli_usage>` carefully.
 
+
 The part of this data structure that describes how to apply the network configuration
 is the 'network_scheme' key in the top-level hash of the YAML file. Let's take a
 closer look at this substructure. The value of the 'network_scheme' key is a hash with

pages/user-guide/cli.rst

@@ -20,6 +20,12 @@ Fuel CLI tool is a powerful tool that allows you to:
 
 Fuel CLI may break your environment if not used carefully.
 
+It is necessary to understand that any modifications done using Fuel CLI
+take precedence over the settings made from the browser.
+Fuel shows a special message to inform you:
+
+.. image:: /_images/fuel-cli-warning.png
+
 .. contents :local:
 
 Basic usage