Testing use of external (i.e., with a different namespace and hence non-dereferenceable)

- Added debug flag, when `true` returns in page SPARQL query as well as
results array

Right now, when http://example.org uses data with namespace
http://another.com
- Every time a SELECT is executed, it will change http://another.com to
http://example.org.
- This is not the case for DESCRIBE/CONSTRUCT
- N-Triples, Turtle and RDF/XML versions works fine so far

Problems:
- No description for new URI in http://example.org
- Not clear how to link URI in http://exampler.org to
http://another.com. Suggestion: `<http://example.org/abc> owl:sameAs
<http://another.com/abc>` . It is no clear __when__ to do it