static DocRef parseDocRef(final String href) {
        return new DocRef(
                getPart("type", href, PipelineDoc.TYPE),
                getPart("uuid", href, href),
                getPart("name", href, null));
    }
Called by the processor when it encounters an xsl:include, xsl:import, or
document() function.

@param href An href attribute, which may be relative or absolute.
@param base The base URI against which the first argument will be made
            absolute if the absolute URI is required.
@return A Source object, or null if the href cannot be resolved, and the
processor should try to resolve the URI itself.
@throws TransformerException Thrown if the referenced resource cannot be found.
stroom-pipeline/src/main/java/stroom/pipeline/xslt/CustomURIResolver.java