Added method get_all_DBAdaptors_by_dbname(), which is very similar to

get_all_DBAdaptors_by_connection():

  Arg [1]    : string, name of database
  Returntype : reference to list of DBAdaptors
  Exceptions : none
  Example    : @dba = @{ Bio::EnsEMBL::Registry
                  ->get_all_DBAdaptors_by_dbname($dbname) };
  Status     : Stable


Some formatting.