Finish PSSE parser

[PhilipFackler]

• Add switched shunts (with place-holders for remaining record types)
• Ensure compliance with v34
• Emit warning in conversion function when elements are present that are not supported by PS
• Handle optional inputs
• Add remaining record types
  • system-wide data
  • area
  • two-terminal dc
  • vsc dc
  • impedence correction
  • multi-terminal dc
  • multi-section line
  • zone
  • inter-area transfer
  • owner
  • facts device
  • gne
  • induction machine