Incluir o XML anotado na interface do Manager #806

- adiciono Prism.js para mostrar o XML.
- balaio: add function to obtain the URL to get the ``pure`` xml of the
package.
- "Hardcoded" xml Uri, to be replaced when Balaio implements the
endpoint (see: issue: scieloorg/balaio#317).
- process the XML file using stylechecker.
- /tests/xml_tests/files/*.xml various xmls files to tests.