Include  filters support for Mapping shortcuts

Mapping shortcuts is a great feature, not only to improve flexibility, this allow a kind of generic query, for example:

``` php
  if ($table=='A'){
    $mapper->tableX = $mapper->tableA;
  } else {
    $mapper->tableX = $mapper->tableB;
  }
  $mapper->tableX(array(...))->tableY->fetch()
```

But mapper do not support filer like this. Primary key works.
