Fixed xml namespaces

I just discovered I did something completely wrong in the XML examples. Instead of:

````xml
<container xmlns="..."
    xmlns:cmf-search="http://cmf.symfony.com/schema/dic/search">

    <cmf-search:config xmlns="http://cmf.symfony.com/schema/dic/search">
        <search-fields
            foo="bar"
        />
    </cmf-search:config>
</container>
````

It should be:

````xml
<container xmlns="...">

    <config xmlns="http://cmf.symfony.com/schema/dic/search">
        <search-fields
            foo="bar"
        />
    </config>
</container>
````

This PR fixes that, I'm going to merge it soon if nobody comments.