[WIP][Cookbook] Document how to install 3th party bundles

cookbook/bundles/index.rst

@@ -9,3 +9,4 @@ Bundles
     override
     remove
     extension
+    installation

cookbook/bundles/installation.rst

@@ -0,0 +1,141 @@
+.. index::
+   single: Bundle; Installation
+
+How to install 3rd party bundles
+================================
+
+Most bundles provide a documentation of installation. However, most
+steps are common for any bundle.
+
+Add composer dependencies
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Starting from Symfony2.1 dependencies are managed via Composer. It's
+a good idea to learn some basics of Composer here:
+http://getcomposer.org/doc/00-intro.md.
+
+Before you can use composer to install a bundle you should look for a
+`Packagist`_ package of that bundle. For example, for the
+`FOSUserBundle`_ you should look for a
+``friendsofsymfony/user-bundle`` package and it does exists:
+https://packagist.org/packages/friendsofsymfony/user-bundle.
+
+.. note::
+
+    Packagist is the main archive for Composer. If you are searching
+    for a bundle, the best thing you can do is check out
+    `KnpBundles`_, it is the unofficial achive of Symfony Bundles. If
+    a bundle contains a README file, it is displayed there and if it
+    has a Packagist package it shows a link to the package. It's a
+    really usefull site to begin searching for bundles.
+
+Now you have the package name, you should determine the version you
+want to use. Usually different versions of a bundle correspond to a
+particular version of Symfony, this should be in the README file (in
+the Package, which you can view on Github or KnpBundles). If it isn't
+in the README, you can use the version you want. In the case of
+FOSUserBundle README file has a caution that version 1.2.0 must be
+used for Symfony2.0 and 1.3 for Symfony2.1+. Let's use development
+version for this exmaple.
+
+Now we can add the bundle to our composer.json file and update the
+dependencies. You can do this manually:
+
+1. **Add it to the ``composer.json`` file:**
+
+   .. code-block:: javascript
+
+       {
+           ...,
+           "require": {
+               ...,
+               "friendsofsymfony/user-bundle": "dev-master"
+           }
+       }
+
+2. **Update the dependency:**
+
+   .. code-block:: bash
+
+       $ php composer.phar update friendsofsymfony/user-bundle
+
+   or update all dependencies
+
+   .. code-block:: bash
+
+       $ php composer.phar update
+
+Or you can do this in one command:
+
+.. code-block:: bash
+
+    $ php composer.phar require friendsofsymfony/user-bundle:dev-master
+
+Enable the bundle
+~~~~~~~~~~~~~~~~~
+
+Now the bundle is installed into our Symfony project (in
+vendor/friendsofsymfony/) and the autoloader recognises this
+bundle. The only thing we need to do now is registering the bundle in
+the AppKernel:
+
+.. code-block:: php
+
+    // app/AppKernel.php
+
+    // ...
+    class AppKernel extends Kernel
+    {
+        // ...
+
+	public function registerBundles()
+	{
+	    $bundles = array(
+                ...,
+                new FOS\UserBundle\FOSUserBundle(),
+            );
+
+            // ...
+        }
+    }
+
+Configure the bundle
+~~~~~~~~~~~~~~~~~~~~
+
+Usually bundles require some configuration to be added to app's
+app/config/config.yml file. Bundle's documentation will likely
+describe that configuration. But you can also get a reference of the
+bundle's config via ``config:dump-reference`` command.
+
+For instance, in order to look the reference of the assetic config we
+can use this:
+
+.. code-block:: bash
+
+    $ app/console config:dump-reference AsseticBundle
+
+or this:
+
+.. code-block:: bash
+
+    $ app/console config:dump-reference assetic
+
+The output will look like this:
+
+.. code-block:: text
+
+    assetic:
+        debug:                %kernel.debug%
+        use_controller:
+            enabled:              %kernel.debug%
+            profiler:             false
+        read_from:            %kernel.root_dir%/../web
+        write_to:             %assetic.read_from%
+        java:                 /usr/bin/java
+        node:                 /usr/local/bin/node
+        node_paths:           []
+        ...
+
+.. _Packagist:     https://packagist.org
+.. _FOSUserBundle: https://github.com/FriendsOfSymfony/FOSUserBundle
+.. _KnpBundles:    http://knpbundles.com/