Added a test suite for the Turtle parser based on the 19 February 2013 Candidate Recommendation
Improve formatting of string literals containg 3 or more " characters in Turtle/N3
Turtle/N3 formatting: improved blank node handling at the loss of some elegance
Added Turtle formatter tests

--HG--
rename : tests/TurtleParserTest.hs => tests/TurtleTest.hs
NTriples: allow mixed-case language tags
Added the runw3ctests executable, built by setting the w3ctests flag
Relax some constraints on creating a Swish.QName.LName
Turtle Formatter: no-longer convert xsd:double values to use a lower-case e for the exponent term
Turtle parser: update to 19 February 2013 CR
Minor doc fixes and additions