Weyl Dimension and related stuff

[riteshksingh]

Additional Feature

The Weyl dimension formula calculates the dimension of a representation using the highest weight and the list of positive roots. The calculation also requires the sum of all positive roots frequently. Thus it makes sense to add delta=sum of positive roots as a data in LieAlgebra/LieGroup class itself. Further, the representation class should first calculate the Weyl dimension of a given representation and make decisions/suggestions in subsequent methods for any further optimization or for bravely giving up the calculation of representation matrix large dimensions.