code: public Iterable<DColumn> getAllColumns(String storeName, String rowKey) {
          return getColumnSlice(storeName, rowKey, null, null);
      }
docs: Get all columns for the row with the given key in the given store. Columns are
  returned as an Iterator of {@link DColumn}s. If no row is found with the given key,
  the iterator's hasNext() will be false.
  
  @param storeName Name of store to query.
  @param rowKey    Key of row to fetch.
  @return          Iterator of {@link DColumn}s. If there is no such row, hasNext()
  will be false.