m = buildEMonomialMap
R and S must be rings created by buildERing. Each orbit of variables in S consists of variables of the form x_{(i_1,...,i_k)} for some width k. L is a list that for each such orbit gives the desired image of x_{(0,...,k1)}. The rest of the map is extrapolated from these value.








If a given variable orbit of S has k indices, then the target monomial list in L should only use indices between 0 and k1.
The object buildEMonomialMap is a method function.