I'm not so sure about editing the data in the DB with external programs, it's rather easy to break the DB consistency that way. Also the DB won't be a real RDBMS engine, just a SQLite file. Still, it should be possible to later add a plugin that overrides the entire system by using data from a RDBMS, if we add the needed hooks.
 
Very well, I'll make that change, then. On a branch, of course.
 
The branch being, of course, master.
 
Anyone good with UI design here? Could you prepare some ideas about what the webadmin should look like for the permission management?
 
I'm not a professional, but this is a sketch I quickly made just to get the discussion started (Excuse my poor handwriting):
 
That's exactly what I wanted. I don't need a profi website, I need to see what's where, what controls, what functions. A diagram is the best, this is even too much (a ruler? 
Now this is a player list with rank control, we need to define the ranks and probably list their groups / permissions, too.
 
 
So far I've come up with the following webadmin schema:
Tab Online players:
  - (pretty much what STR_Warrior drew, without the Offline players section)
  - per-world list of players
    - name
    - position (?)
    - rank
  - can change each player's rank
  - can kick each player
  - can view list of player's permissions
  - can send PM
  - special "Player details" subpage?
Tab Ranks:
  - (more or less done in the PR)
  - displays list of ranks
  - add / rename / delete a rank
  - add / remove groups to ranks
  - set rank visuals
  - view all players in a rank (?)
Tab Permissions:
  - displays list of groups
  - add / rename / delete a group
  - add / remove permissions to groups
I've split the ranks / permissions into separate pages, because there will be possibly a lot of entries in each and two long lists on a single page would be impractical.
 
That's about what I had in mind as well + allot of usefull extras, but I don't think the players position is needed in the Online Players tab. Could that go in the "Special player details subpage"?
EDIT:
Maybe even an TP to player/coordinates button?