Support mybatis:bind like as <bind>

In current feature, it does not support for binding new variable like as `<bind>` provided by xml based scripting language.

I hope to be enabled to write as follow:

```sql
/*[# mybatis:bind="firstNamePattern=|%${firstName}%|" /]*/

SELECT * FROM names
  WHERE firstName LIKE /*[('#{firstNamePattern}')]*/ '%Ta%'
```

### Tasks

- [x] coding
- [x] testing
- [x] documentation
