Made 'create-user' command consistent.

There is a very minor inconsistency between the naming of the 'create users' command at the beginning of the document and the 'create user' command for the rest of the article. It starts with the plural, then changes to singular. A very minor thing, but when you're following the documentation precisely, this inconsistency raises unnecessary questions. Updated all references to 'create-user'.

Author: Jonathan Finch

console.rst

@@ -50,14 +50,14 @@ method. Then you can optionally define a help message and the
     {
         $this
             // the name of the command (the part after "app/console")
-            ->setName('app:create-users')
+            ->setName('app:create-user')
 
             // the short description shown while running "php app/console list"
-            ->setDescription('Creates new users.')
+            ->setDescription('Creates a new user.')
 
             // the full command description shown when running the command with
             // the "--help" option
-            ->setHelp('This command allows you to create users...')
+            ->setHelp('This command allows you to create a user...')
         ;
     }
 
@@ -68,7 +68,7 @@ After configuring the command, you can execute it in the terminal:
 
 .. code-block:: terminal
 
-    $ php app/console app:create-users
+    $ php app/console app:create-user
 
 As you might expect, this command will do nothing as you didn't write any logic
 yet. Add your own logic inside the ``execute()`` method, which has access to the