Transfer nested-Keplerian data to transit model

[dmuley]

Need to create a function to move sky-projected xy-coordinates from the nested Keplerian model into the polar integration module. Such a function would have to account for a number of factors, including:

• Which bodies are stars (emitting detectable light) and which are not, in order to apply the procedure for each star rather than just for one.
  • Ensure correct ordering of bodies (planets behind a star should not count towards the amount of light blocked) and eliminating non-intersecting bodies.
  • Not performing unnecessary steps that do not contribute to the final light curve.

[dmuley]

Issue resolved although efficiency improvements sill needed.