Not yet working formulation of comparison chains
Cleaned up the simple rendering functions, added general data types for chains such as equations.
Added test for equation chains and some more reasonable approximation for floats
Removed the 'argToEnclosed' MathPrimitiveId thing. This was intended for giving a symbol argument to e.g. a sum, as the summation variable. But it doesn't seem to have any advantage over an ordinary lambda (or maybe it has; need to try that out now).
Implementation of "sum-over-list" typechecks, now need something to generate lists...
Added simple list-set-generator and test for sums over such sets, which appear to work nicely.