[7.1] Release Notes: Pretty-printing XML validation errors

Toby Crawley from Bob McWhirter's team has developed a small library for creating nicer feedback messages when xml parsing errors are found, based on analysis of the xsd.[1] He has done some work on integrating this library into WildFly for parsing the server/domain config documents and has proposed adding it in.[2] This looks like a good thing to do from the community side, but since doing it there means it will likely appear in EAP 7.1 and it will noticeably affect user experience during boot if the user presents an invalid configuration document, we'd like to get QE involvement with it, so I am adding it to the EAP7 kanban.

[1] http://post-office.corp.redhat.com/archives/jboss-tag-public/2016-June/msg00016.html
[2] http://lists.jboss.org/pipermail/wildfly-dev/2016-July/005280.html