Better position types, newtypes for time, more position calculations, some utils

BREAKING CHANGE: the Coordinates type has been retired, in favor of the more specific
GeographicPosition and EclipticPosition. calculateCoordinates is now calculateEclipticPosition,
and the calculateCusps* family now takes a GeographicPosition as part of its inputs.

• Introduces an Internal module with types and helpers that this library introduces,
  which are not native to the underlying C library. Import at your own risk! (the "curated"/
  "stable" ones are re-exported by the main module.)
  • Deprecates the Coordinates type, in favor of EclipticPosition.
• Introduces functions to calculateEquatorialPosition and calculteObliquity at a given time,
  as well as types that better convey the different types of positions (EquatorialPosition, ObliquityInformation).
• Some astrology helpers: convert between equatorial and ecliptic (and vice-versa,)
  obtain the Delta Time effective at a given moment, obtain the house position of a given body.
  (Note: the calculateHousePosition function is more useful for working near the polar circles or for bodies
  off of the ecliptic -- the ARMC and obliquity need to be calculated or provided, it's simpler
  if you already have the cusps: just check which cusps a given longitude falls between -- no need for
  this function!)