more strict rules for italic emphasis to avoid file name clashes

this additional check avoids /root/.hiddendir from italicising /root/,
because that is often used in path names
Syntax documentation rewrite for M-commands

Rewrote the syntax documentation for all commands starting with the
letter M.
Merge pull request #90 from ailin-nemui/italics-exception

more strict rules for italic emphasis to avoid file name clashes
Syntax documentation rewrite for N-commands.

Rewrote the syntax documentation for all commands starting with the
letter N.
Removed the obsolete NOTE command

I removed the binding for the NOTE command that doesn't exist anymore on
any major network.
Implement CAP Related Signals
barely fix make dist
Add a setting to configure rejoin on reconnect behaviour