Bulk insert / Batching
Enhancement to add bulk editing and batching 
bulk insert statement
```
type
    User2 = object
       age: Positive

withDb:
 let users: seq[User2]
 users.add(User(age=2))
 users.and(User(age=2))
 users.add(User(age=2))
 users.save()
```
which would execute
```
INSERT INTO user2 (age) VALUES (?, ?), 
(2),
(2),
(2);
```

Batching
*could just have this and map over prepare() and then db.save() instead of the bulk example above
```
type
    User2 = object
       age: Positive
type
    Book = object
       age: Positive

withDB:
  var user = User2(age: 1)
  user.prepare()
  var book = Book(age: 1)
  book.prepare()
  db.save()

```

which would execute one sql

```sql
INSERT INTO user2 (age) VALUES (?, ?), 
(1),
INSERT INTO book (age) VALUES (?, ?), 
(1),
```

