Lax validation creates conflicts over plugin content

Xerces has a broken interpretation of lax validation, and allows nested instances of laxly validated elements to themselves be skipped. This masks a problem where a built-in global element in the config schema conflicts with a one-off element name used inside a plugin. Simple example is the Path element from the RequestMap conflicting with the Path element used in the File-based CredentialResolver plugin. This fails validation in most tools, but passes Xerces.