Fix VersionMatchType definition

[cdanger]

In #41 , we established that the new VersionType pattern in the XSD would be
(0|[1-9]\d*)(\.(0|[1-9]\d*)){0,3}
So the corresponding new VersionMatchType pattern would be:
(0|[1-9]\d*|\*)(\.(0|[1-9]\d*|\*|\+)){0,3}

(The old XACML 3.0 VersionMatchType pattern is ((\d+|\*)\.)*(\d+|\*|\+) )