/icon enhancements:
* removed clienttag from the command syntax
* simple syntax for normal user: /icon [code]
* complex syntax for operator/admin: /icon set|add|del|list [username] [code]
* add aliases for icon codes in icons.conf (users can use alias name instead of code)
* refactoring customicons function names https://github.com/HarpyWar/pvpgn/issues/10