#1295 Bugfix: Only dense scalars are treated as slices
#1295 Removed now unsupported indexing.
A[IMatrix, IMatrix] now works like A[vector, vector]. @jgillis - please inspect.
#1295 B in A(i,j)=B is transposed if needed
#1295 B in A[i]=B is transposed if needed
#1295 B in A.nz[i]=B is transposed if needed (Matrix)
#1295 Refactored MX::setNZ