Fix ManyManyList#removeAll With Filters

Currently if you do:

    $this->ManyMany()->filter(...)->removeAll()

it will fail, as the fields referenced by the filter are removed by the custom query mangling. This is solved in two parts:

* Allow setting a table target to delete with `SQLQuery#setDelete()`.
* Use the original query in remove all, just set it to delete form the join table.