Provide support for MathObject in evaluation points

[SchmidtNikolas]

List objects cannot be marked as ordered for answer-checking, evaluation points cannot be specified for Formula objects. Evaluation points seem to be necessary for formulas involving factorials. A nice way to fix this is by replacing normal GUIWorK variable declarations with ones such as the following, which effectively limit WeBWorK's equality testing on these variables to integer values within a limited range, e.g.:

Context()->variables->add(r=>['Real', limits=>[1,20],

resolution=>1]);

Context()->variables->add(n=>['Real', limits=>[1,20],

resolution=>1]);

Alternatively, evaluation point syntax can be used, assuming only one real variable n is declared in the variable Context:

$f = Formula("5n!");
$f->{test_points} = [[0],[1],[2],[3],[4]];