Support token filter

This change supports token filter in index comment and table comment.

* Example
```sql
CREATE TABLE Terms (
term VARCHAR(64) NOT NULL PRIMARY KEY,
is_stop_word BOOL NOT NULL
) COMMENT='default_tokenizer "TokenBigram", token_filters "TokenFilterStopWord"' DEFAULT CHARSET=utf8;
CREATE TABLE Memos (
id INT NOT NULL PRIMARY KEY,
content TEXT NOT NULL,
FULLTEXT INDEX (content) COMMENT 'table "Terms"'
) DEFAULT CHARSET=utf8;
INSERT INTO Terms VALUES ("and", true);
INSERT INTO Memos VALUES (1, "Hello");
INSERT INTO Memos VALUES (2, "Hello and Good-bye");
INSERT INTO Memos VALUES (3, "Good-bye");
SELECT * FROM Memos
WHERE MATCH (content) AGAINST ("+\"Hello and\"" IN BOOLEAN MODE);
id      content
1       Hello
2       Hello and Good-bye
```

Please refer to the following changes of Groonga.

https://github.com/groonga/groonga/pull/209