Support multiple databases?

```mysql
mycli> USE db1
mycli> SELECT * FROM db1.tb1 t1  JOIN db2.tb2 t2 ON t1.<cursor_1>= t2.<cursor_2>
```

cursor_1 can auto complete, but cursor_2 nothing shows.

```mysql
mycli> SELECT * FROM <cursor_3>
```

cursor_3 doesn't show anything about my databases, mycli just show the table name from my connection( mycli mysql://user:pwd@127.0.0.1:3306/db_dev)
