Demonstration program for using CAS with PPL

[Han]

Oh, I misunderstood the use of m0, then. I thought it was just a temporary result, so I took it to the extreme and made everything local variables. :-)

I adjusted the code to enable users to save the matrix as any CAS variable in the main program, or they can choose to also not save the result (by pressing [Esc]). Beam2_Solve() will still work whether or not the parameter 'matrix' is a string. I suppose it still has a minor drawback in that now you have to also specify which matrix to use when doing repeated calls.