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