Adding warn command to warn users blandly



Adding a warn command that warns a specific user using an
alert box, so he knows he's doing wrong and that he might
be kicked or worse. This warn is pretty much harmless, but
it won't kick you out of battle and the moderation action
message shown everyone in the chat will let everyone
watching know that that user was doing wrong and that
they should not do the same to keep being a positive -or a
not negative- chat presence.
This action is logged in the user's modlog and is thus easy
to track the punishment scale he is receiving, should he
keep disregarding the rules, and it's also easy to mark
troublesome users as warned to be harsher to them upon a new
bad action on a different day.
Users that are warned can not longer advocate that they didn't
see the chat -which might be true on some time zones- or that
they missed the PM.