Make the sparse matrix printer pretty
What does this implement/fix?
This makes the operator<< for sparse matrices have a fixed width.
Consider the matrix:
2.00 0.00 0.00
0.50 1.66 0.00
0.50 -0.15 1.31
When I print this using the current operator<< it looks like this:
2.00 0 0
0.50 1.66 0
0.50 -0.15 1.31
My fix to this operator enforces a variable width so that it would look like this:
2.00 0.00 0.00
0.50 1.66 0.00
0.50 -0.15 1.31
Now it actually looks pretty print_matrix) does something similar, though the implementation is different.