Add support for fuzzy search

[kou]

Groonga provides fuzzy search feature (as an experimental feature) since 13.0.8.

We can add an option to enable fuzzy search for Japanese.

We need to do the followings to enable fuzzy search for Japanese:

• Create needed PGroonga index(es) with TokenMecab
• Add --fuzzy_max_distance_ratio 0.34 option to select (Groonga's select not SQL's SELECT)