FIX TestSemanticURIGuesser

TODO fails on http://fcns.eu/people/andrei/card#me
because no clue except looking into content, or maybe using the presence of #
NOTE: Files.probeContentType(url) returns null with Java JRE 7, OK with 8
Scala: add capability to specify properties - now tested in TestCreationForm2

TODO : introduce capability in Play! app; write properties lists for main classes : foaf:Person, foaf:Document, foaf:Project, ...