anchor.diff:  Returns *false* if '$name' is a group name in use already in the database, otherwise *true*.
   
   
  -=== Instance methods
  -
  -==== getID() : int
  -
  -Returns the unique *id* of the group.
  -
  +=== Description
   
   ==== getDescription() : string
   
  
positive.code: Updates the group's *description* in the database.
  Throws a *GroupException* with code *204* if '$description' is invalid.
  See *validDescription()* for more details.
  
  
  ==== addMember(User $user) : void
  
negative.code: ==== getUserGroups(User $user) : array
  
  Returns an array of *Group* objects representing all groups which '$user' is a member of.
  
  
  ==== setupDB() : void
  