- added new ARCANGLETO command needed for PPTX custom shapes import
  - added added placeholder for unimplemented QUADRATICCURVETO command,
    skip it's data at least so that we don't break other things for now
  - cache equations results to optimize custom shapes calculation
    PPTX import creates such equations that made system busy for long
    time, this removes that issue
  - added lot of debug output to help with debugging of complex imported
    custom shapes