-Added coordinate type check (infra inherits ultra)
-Redid get_location(T_STRING) to be more generic.
-Added string() to all classes
-Added magnitude() to all classes
-Added convert() to all classes TODO: Make this less duplicative?
-Fixed conversion of Cartesian to Spherical because I was stupid before.
-Added basic vector arithmetic to the abstract
-Added a loop to read children of $universe.
-Added some trivial vector arithmetic test cases.