Added CardInfo root element to all XML files, closes #136.
Removed debug strings in the XmlCardLoader class.
Fixed typos in exception messages in the XmlCardLoader class.
corrected `CannotUseUnknownCards` system
Renamed `CannotUseUnknownCards` to end with `System`
Merge branch 'develop' of github.com:Cardshifter/Cardshifter into client-server
Merge branch 'javafx' of github.com:Cardshifter/Cardshifter into client-server
fixed sporadious bug in game test. Fixes #134