The Commit For Server Security

> Added saftey for servers that do not want maps downloaded 
> @Vareide @Clankstar @jollyolbrits @OvercastNetwork @ItsHarry @lazertester


Some servers have maps that they do not want downloaded (Example: TheHives SG6).
This commit allows server admins to be able to secure their maps and make sure they don't get released to the public unless they want them to. 

**The security is disabled by default and it requires the server admin to add one of the two codes below to their server.properties MOTD.**

- \u00A7-
- \u00a7-


**TODO**
- [x] Use MOTD to allow server admins to keep worlds private.
- [ ] Instead of sending a message to the users chat, just disable the button.
- [ ] Read from in-game MOTD 
- [ ] Maybe send message through plugin channels to server admins telling them that user has World Downloader Mod if a certain plugin is installed ?????? Not entirely sure.