Add some documentation of DS configuration to the AS 7 User Guide

Need some docs on how to install a datasource in the AS 7 User Guide (or in a page linked from it), since it's such a common use case.

A lot of the details can come via reference to the Iron Jacamar docs, but there are some AS-specific details that should be described; e.g. the two alternatives for getting the driver installed (as a deployment or as a module), and the usage of the <module> element.