The WMSDescribeLayer format currently differs from other formats that
inhreit from VersionedOGC by having an array instead of an object as return
type. This especially bad since the VersionedOGC superclass sets a version
property on the array. With this change, the WMSDescribeLayer format will
also be compatible with GeoServer's new JSON response type for
DescribeLayer - see
http://sourceforge.net/mailarchive/message.php?msg_id=29912776.
Another change included here is the removal of the WMSDescribeLayer
format's getVersion hack, which was replaced by a generic fallback to less
generic parsers, e.g. from a v1_1_1 parser to a v1_1 parser if v1_1_1 is
not implemented.
