don't derive from RationalBasisEJA or its as-yet-nonexistent
element class.
-6. Drop "FiniteDimensional" everywhere.
+6. Add special det/trace method overrides for the algebras where we
+ know them? The only reason this might be tricky is because the
+ obvious solution is to subclass EJAElement, but then we might
+ collide with e.g. the Cartesian product element subclass.