function ColPermute(const Src: TMtxInt; const PermuteIdx: TVecInt): TMtxInt;
Permute the columns of the Src matrix.
Result: stored in self (calling object), returns self for chaining
Remarks:
The parameter PermuteIdx contains indexes of columns P[i] to which column at Index "i" is to be moved. The result of the permutation is stored in the calling matrix. Only entire matrix can be copied.