ENH: expand multicol_align and multirow_align Styler.to_latex

[attack68]

Currently styler only allows multicol_align in {"r", "l", "c", "naive-l", "naive-r"}

Simple pipe characters around multicol_alignment allow dividers to be drawn, e.g. |r or |r| or r| etc..

\begin{tabular}{lllrrrrrr}
\toprule
{} & {} & {} & \multicolumn{3}{|r|}{1} & \multicolumn{3}{|r|}{2} \\ 
{} & {} & {} & \multicolumn{2}{r|}{a} & {b} & \multicolumn{2}{|l}{a} & {b} \\
{} & {} & {} & {0} & {0} & {0} & {0} & {0} & {0} \\
\midrule
\multirow[t]{3}{*}{1} & \multirow[t]{2}{*}{a} & 0 & -1 & -1 & -1 & -1 & -1 & -1 \\
 &  & 0 & -1 & -1 & -1 & -1 & -1 & -1 \\
 & b & 0 & -1 & -1 & -1 & -1 & -1 & -1 \\ \cline{1-3}
\multirow[t]{3}{*}{2} & \multirow[t]{2}{*}{a} & 0 & -1 & -1 & -1 & -1 & -1 & -1 \\ 
 &  & 0 & -1 & -1 & -1 & -1 & -1 & -1 \\ 
 & b & 0 & -1 & -1 & -1 & -1 & -1 & -1 \\
 \bottomrule
\end{tabular}

Also note the cline (this one might be harder to implement)