Tiny enhancements proposal

[HJarausch]

I'd like to propose tiny enhancements (see attached file)

1. Sometimes one needs a matrix of dimension 0x0 - it's easy to check for this special case
2. In Matlab/Octave one can write zeros(X), ones(X) and eye(A) where X is a Vector or a Matrix, and A is Matrix
3. Given a matrix A, it's very convenient to operate on its columns like A[j]= A[j]-A[j-1]. On the rhs this is just an alias for column whereas there is no such thing for the lhs currently

Thanks for adding this to neo. I can't imagine any conflict with existing code.

Neo_EP.nim.txt