Implement join and quit messages

[mdcfe]

Implement join and quit messages:

• The join and quit messages are defined in the locale
• The permissions neutron.silentjoin and neutron.silentquit can be used to hide join and quit messages for a player if connectmessage.allow-silent-join-quit is set to true in the config

I've taken the locale code from CommandWrapper, but I think this should be moved to reside with the locale code itself rather than being duplicated here.

Feel free to push any changes here as needed.

[Crypnotic]

Latest commit has the locale getMessage and message statically accessible in StringHelper

[mdcfe]

@Crypnotic The original commit was replaced with a8124c6 which uses StringHelper.

[Crypnotic]

@md678685 source.sendMessage(getMessage()) can be replaced with message() no?

[mdcfe]

@Crypnotic StringHelper doesn't have an equivalent for broadcast. I'll update #19 to use message though.

[Crypnotic]

I've added a StringHelper#broadcast that translates locale for each player based on the locale configuration, but I'll just merge and make a few changes that I would like to see that are based more on preference to keep you from having to do them