cleaned up MultivariatePolynomial
cleaned up MultivariatePolynomial

Currently, the input  2^(1/2)+3^(1/2)+(5+2*6^(1/2))^(1/2) runs into a bottleneck in the form of the numerical approximation code calling Integer.Exponentiate on a large integer with a fractional exponent. The method by which the integer is tested for perfect-power factors is naive.
AlexanderKindel/solver,AlexanderKindel/solver