Initial commit for ISS Orbit

1. TLE for ISS is from https://celestrak.com/NORAD/elements/stations.txt
2. SGP4 Model http://celestrak.com/NORAD/documentation/spacetrk.pdf
3. TLE definitions
http://spaceflight.nasa.gov/realdata/sightings/SSapplications/Post/JavaSSOP/SSOP_Help/tle_def.html
ISSOrbit prints Sun-ISS vectors

TODO(satayev): revert this commit after the presentation.
Sunlight
Revised code for Ricardo
ISSOrbit now returns Vector for photon's direction based on time
AbsorptionSimulation works with ISSOrbit
ISSOrbit implemented in AbsorptionSimulation