First commit of the UI portion of Akarsh's Conjunctions predictor. Congratulations, Akarsh! Thanks for this great contribution.

For now, the tool is implemented as a calculator module (and maybe it makes sense to keep it there).

TODO:
+ Allow the user to set the maximum angular separation for considering a conjunction
+ (Bug) Remove "Earth" from the list of solar system bodies
+ Friendlier string formatting of Date/Time in results
+ Allow for selection of comets and asteroids
+ (my wishlist item) Allow second body to be any SkyObject, not just solar system bodies.