FUNCTION: LieTools/SgMonoCoeff
USAGE: SgMonoCoeff(gpoly,mono); 
SYNOPSIS: SgMonoCoeff(gpoly,mono) returns the (constant) coefficient of 
  the monomial mono of a element gpoly in S[g]. 
EXAMPLE: 
> SgMonoCoeff(3*g[1]^3+2*g[1]^2 + g[1] + 23*g[2]*g[3],g[1]^3);

                                  3

> SgMonoCoeff(3*g[1]^3+2*g[1]^2 + g[1] + 23*g[2]*g[3],g[1]^2);

                                  2

> SgMonoCoeff(3*g[1]^3+2*g[1]^2 + g[1] + 23*g[2]*g[3],g[2]*g[3]);

SEE ALSO: LieTools[SgPolySplit], LieTools[PolySplit]
