Reject more invalid usernames from clients.

Specifically this should cover people connecting with a username of
"\u200C"
Merge branch 'master' of git://github.com/mbruker/Cockatrice
Fixed duplicate case compile error
Merge pull request #2 from VanNostrand/RespUsernameInvalid-fix

Fixed duplicate case compile error
Added internet howto for own server on CentOS.
Added FAQ from cockatrice wiki.
Added shortcuts documentation.
Added documentation/howto for card database.
Added current sets.xml
Merge pull request #3 from VanNostrand/documentation

Documentation-Branch