Log Message: 
Implements a Parser context in which only polynomials (of a single
variable) can be entered. Only sums of multiples of powers of the
variable are allowed to be entered (though the coefficients can
contain mathematical operations). An optional flag lets you specify
that only one term of each degree is allowed, so the student would
have to combine 1+x+x+x^2 to get 1+2x+x^2 in that case.
