Extensive rewrite of parser from Turtle's official BNF grammar (from w3c.) Beaver now passes the official test.nt file, but variables are currently broken.
Fixing string handling.
Fixing @for expressions, and disambiguating function patterns/collections.
Fixing single variable definitions.
Better differentiation between variables and functions.
Check for variables in subject.
Fixing ambiguity in function calls.
Require entire document to be parsed using parseString(parseAll=True) instead of scanString.
When calling a function, check if arguments are variables first.
Un-commenting this line. The only test that fails now is parsing the entire test.nt document.
Enabling datatype strings; the datatype is internally ignored currently, but is still correctly parsed. test.nt can be successfully parsed now.