Fixed assert in Matrix::setDimensions to allow zero dimensions

void Matrix< Real, Device, Index, RealAllocator >::setDimensions( const IndexType rows,

                                                   const IndexType columns )

{

   TNL_ASSERT( rows > 0 && columns > 0,

   TNL_ASSERT( rows >= 0 && columns >= 0,

               std::cerr << " rows = " << rows << " columns = " << columns );

   this->rows = rows;

   this->columns = columns;