Better escape commands

[Infernio]

As it stands, the current idea is to have escapes like

\lbracket # -> [
\rbracket # -> ]
\semicolon # -> ;

With some shortcuts. Better would be:

\[
\]
\;

I still want to have bare semicolons outside commands (#31), but this would make writing escapes for other reserved symbols much easier (plus semicolons inside commands).