Fixed handling of public and system IDs.

The IDs are now correctly obtained from the source XML document and passed to
the transformer before the target document is written.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/branches/immutableNodes@1585187 13f79535-47bb-0310-9956-ffa450edef68
Fixed some failing test cases.

git-svn-id: https://svn.apache.org/repos/asf/commons/proper/configuration/branches/immutableNodes@1585188 13f79535-47bb-0310-9956-ffa450edef68