Pass a raptor_term for subject to raptor_ntriples_generate_statement

(raptor_ntriples_parse_line): Make term here and pass to
raptor_ntriples_generate_statement subject
Pass a raptor_term for predicate to raptor_ntriples_generate_statement
Pass a raptor_term for object to raptor_ntriples_generate_statement
Pass a raptor_term for graph to raptor_ntriples_generate_statement
Make URIs in one place during syntax parsing
Make literals once during syntax parsing

Move language normalization to same area of code
Kill use of terms, term_lengths and term_types
Move object_literal_language/datatype to area of code that uses it.
Check for illegal unicode escapes.
Check for bad URIs using turtle function - FIXME
(raptor_uri_string_is_absolute): Added
Use raptor_uri_string_is_absolute to enforce abs URIs for N-Triples
Use raptor_uri_string_is_absolute to check datatype URI is abs
Check language tag validity