anchor.diff:  Updates the lock's *description* in the database.
   Throws a *LockException* with code *304* if '$description' is invalid.
   See *validDescription()* for more details.
  +
  +
  +==== Lock::validDescription(string $description) : bool
  +
  +Returns *true* if '$description' is a valid lock description, otherwise *false*.
  +Validity is determined by a regex loaded from the *description_regex* parameter in the *[lock]* section of config files.
  +
  +
  +=== Instance methods
  +
  +==== $lock->getID() : int
  +
  +Returns the unique *id* of the lock.
   
   
   ==== $lock->grantGroupKey(Group $group) : void
  
positive.code: ==== Lock::getByID(int $id) : ?Lock
  
  Returns a *Lock* representing the lock referenced by '$id', or *NULL* if no lock with that id found.
  
  
  ==== Lock::validDescription(string $description) : bool
  
  Returns *true* if '$description' is a valid lock description, otherwise *false*.
  Validity is determined by a regex loaded from the *description_regex* parameter in the *[lock]* section of config files.
  
  
  ==== Lock::setupDB() : void
  
negative.code: Returns *false* if '$name' is a lock name in use already in the database, otherwise *true*.
  
  
  === Description
  
  ==== $lock->getDescription() : string
  
  