Add some xml and php formats

This PR added XML formats in the `reference/configuration` section for the AsseticBundle, WebProfilerBundle and SwiftMailerBundle. It also adds the XML and PHP formats for the `Min` constraint.

It's my first time that I use xml or PHP for configuration, so I'm not sure about all of them. Please check the examples before merging.<br>
I don't know the schema location and how this should be registered, this should be added before merging.

If this PR is correct and gets merged, I will create the other missing formats in the reference section too.