Documentation-Branch

I'd like to have a better documentation, especially with coding, building and packaging information and a usermanual in the future.
So I added a doc directory which at the moment contains some information from the cockatrice.de dokuwiki like the FAQ, shortcuts and added some howtos I found in the internet like a servatrice installation howto for CentOS and how to manually create/update the card database.
I could think of porting the wiki entries to a LaTeX/pdf manual and add it to the doc directory if you like the idea.