Scala: FIX BrowsableGraph.focusOnURI was getting too many triples ; add TestBrowsableGraph
Scala: add route /sparql (not yet in HTML UI)

tested with
http://localhost:9000/sparql?query=CONSTRUCT%20{?g%20%3Cp%3E%20%3Cv%3E%20.%20}%20WHERE%20{graph%20?g%20{%20%20?s%20?p%20?o.%20%20}%20%20.}
Play! FIX Turtle dowload ; TODO also get reverse triples in other graphs
FIX query for download (BrowsableGraph.scala), update missing features in README.md, update example.form.foaf.html