Fix relationship record retrieval

If a custom filter condition is supplied to any of the With{Type} methods the foreign key condition is not actually added to the query. While this doesn't break the retrieval it does pull a lot of unnecessary data into memory.

For a type A that has a 1:N relationship to type B the queries look like these:
```sql
SELECT __a.id, __a.c_id FROM a __a LIMIT 1 OFFSET 0;

SELECT __b_Other.id, __b_Other.attribute, __b_Other.a_id FROM b __b_Other WHERE __b_Other.attribute = $1;  -- current
SELECT __b_Other.id, __b_Other.attribute, __b_Other.a_id FROM b __b_Other WHERE (__b_Other.attribute = $1 AND __b_Other.a_id IN ($2)); --fixed
```

```golang
type A struct {
	kallax.Model
	ID    int64 `pk:"autoincr"`
	Other []B
}

type B struct {
	kallax.Model
	ID        int64 `pk:"autoincr"`
	Attribute int64
}
```

Author: ligustah

batcher.go

@@ -175,7 +175,7 @@ func (r *batchQueryRunner) getRecordRelationships(ids []interface{}, rel Relatio
 
 	filter := In(fk, ids...)
 	if rel.Filter != nil {
-		And(rel.Filter, filter)
+		rel.Filter = And(rel.Filter, filter)
 	} else {
 		rel.Filter = filter
 	}