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
New LaTeX usermanual: added first pt. from cockatrice.de dokuwiki
fixed the github url
Updated sets.xml - maybe it is too complete now.
Added script that generates sets.xml output
Completed "Getting Started" of the Usermanual.
Smooshed subtly separate bullets lists into single lists
Changed inline code formatting to block code formatting
Changed some paragraph splits to proper line breaks
Merge pull request #5 from skoh-fley/master

Various Markdown fixes in README.md
Added chapter Playing Online