Release 3.1.4

• Update cast to datatype based on XPath 3.1 https://www.w3.org/TR/xpath-functions/#casting-to-string
• Make Query::Pattern#executable? return true.
• Import some extensions from rdf-n3.
• Query#optimize! must preserve graph_name.
• For SPARQL*:
  • Update result formats for JSON and XML to use "subject", "predicate", and "object" for embedded triples, instead of "s", "p", and "o", as is becoming normal behavior.
  • Add proposed CSV and TSV formats for embedded triples.
  • Support {| ... |} annotations in CONSTRUCT and WHERE.
• Escape nl, tab, and cr in TSV results.
• Use logger instead of built-in debug output.
• Fix setting port to run on in sparql CLI.