#591 Improved position information for CIF invariants

• Position information for invariants has been improved:
  • Use position of the name if available.
  • Use position of the invariant declaration otherwise.
    • Invariant declaration prefers to use the position information of the invariant keyword, and otherwise uses the position information of the supervisory kind keyword.
  • No longer uses the position of the predicate or the needs/disables keywords.
• Best to review per commit.

Closes #591 (closed)