Remove old commands and unused code from sty file

[LSinev]

inspired by https://www.ctan.org/pkg/l2tabu and https://www.ctan.org/pkg/nag

• Little bit of code formatting changes.
• Removed commented out or turned off (with \iffalse) code.
• Changed to use of \bfseries, \rmfamily.
• Changed to use of \begin{center}\end{center}.

This increases stability in future use, I hope. Visually, there is no changes (tested even with TexLive 2014 at overleaf) in resulting PDF.

Quote about obsolete \bf from translated l2tabu:

Obsolete commands do not support LATEX 2ε ’s new font selection scheme, or NFSS. {\bf foo}, for example, resets all font attributes which had been set earlier before it prints foo in bold face. This is why you cannot simply define a bold-italics style by{\it \bf Test} only. (This definition will produce: Test.) On the other hand, the new commands \textbf{\textit{Test}} will behave as expected producing: Test. Apart from that, with the former commands there is no ‘italic correction’, cf. for instance halfhearted ({\it half}hearted) to half hearted (\textit{half}hearted).

About obsolete \centerline:

The \centerline command is another TEX command you should not use. On the one hand \centerline is incompatible with some LATEX packages, such as color.sty. On the other hand the package may yield unexpected results.