Whoops !
Revert "The DAV: xml namespace no longer converts to urn:DAV."

This reverts commit 407d42e03b717a04345956ef3fc406be6ae7bbbb.

Conflicts:
	ChangeLog
	lib/Sabre/DAV/XMLUtil.php
Updated changelog and bumped versions.
Merge branch '1.7' into 1.8

Conflicts:
	lib/Sabre/CalDAV/CalendarQueryParser.php
	lib/Sabre/CalDAV/Plugin.php
	lib/Sabre/CalDAV/Version.php
	lib/Sabre/CardDAV/Version.php
	lib/Sabre/DAV/Server.php
	lib/Sabre/DAV/XMLUtil.php
	tests/Sabre/DAV/XMLUtilTest.php
Bumped versions.
A few more urn:DAV related changes
Merge branch '1.7' into 1.8

Conflicts:
	lib/Sabre/CalDAV/Property/Invite.php
	lib/Sabre/CalDAV/SharingPlugin.php
	lib/Sabre/DAV/Locks/Plugin.php