Document WebDAV feature in EAP 7 as unsupported

Per PMs comment https://issues.jboss.org/browse/JBEAP-1036?focusedCommentId=13108900&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-13108900 the WebDAV functionality shall be left out from EAP 7.

It needs to be documented, marking this JIRA as blocker for documentation as this is missing feature and as such it should be documented. There should be also documented reasons why it was left out.