Added "pmute" and "pmuteid".

Updated addon.txt
Removed notification on playerjoin/playerleave
Bugfix: Message for "slap next round" wouldn't show up on removal due to how I placed the log.
Added "ulx steamid" to copy a target's Steam ID.
Updated addon.txt.
Fixed very minor and unaffected issue.
Changed wording of "help" for "ulx steamid".
Merge branch 'master' of https://bitbucket.org/Decicus/ulx-commands-by-decicus