message: Add cost_offset to aux_dictionary
diff: """A tool to generate aux_dictionary.txt from aux_dictionary.tsv.
  * Create a dictionary with entries of key and value in the TSV file.
  + + Fields: [key, value, base_key, base_value, cost_offset]
  * lid, rid and cost are copied from entries of base_key and base_value.
  +* cost_offset adjusts the cost copied from the base entry. If the cost_offset
  + is -1, the new entry is ranked higher than the base entry.
  gen_aux_dictionary.py --output aux_dictionary.txt
  --aux_tsv data/oss/aux_dictionary.tsv
  @@ -89,13 +92,14 @@ class AuxDictionary():
  for line in open(aux_tsv, encoding='utf-8'):
  if line.startswith('#'):
  continue
  - key, value, base_key, base_value = line.rstrip().split('\t')
  + key, value, base_key, base_value, cost_offset = line.rstrip().split('\t')
  for data in self.dictionary.GetDataList(base_key, base_value):
  base_lid, base_rid, base_cost = data
  if self.dictionary.Exists(key, value, base_lid, base_rid):
  # Not overwrite the existing entry.
  continue
  - self.aux_list.append([key, base_lid, base_rid, base_cost, value])
  + cost = int(base_cost) + int(cost_offset)
  + self.aux_list.append([key, base_lid, base_rid, str(cost), value])
  def WriteFile(self, output):
  with open(output, 'w', encoding='utf-8') as file:
  