[with patch] add spacing in latex output of matrices for increasing readbility

[pdenapo]

Currently, printing of matrices in Latex form is difficult to read. I'm submitting a (trivial) patch that adds more spacing to increase readibility.

Example:

sage: M=MatrixSpace(QQ,2,2)
sage: A=M([[2,3],[4,5]])
sage: latex(A)

currently gives:

\left(\begin{array}{rr}
2&3\\
4&5
\end{array}\right)

My patch changes this to

\left(\begin{array}{rr}
2 & 3 \\
4 & 5
\end{array}\right)