Add FTS support

I added FullText Search support in ActiveRecord. It's basically a flag in the table annotation.

```java
@Table(name = "posts", id = BaseColumns._ID, fts = "4")
public class Post extends Model {
   //...
}
```

Here "4" is just the version of the FTS engine. Behind the scene it creates a virtual table instead of a normal table if this flag is used.

PS: My editor screwed some lines converting TABs into spaces. There's a good reason not to use TABs to indent code!!