make Builder::elemMatch acting on select, not only on query

[abmar]

hi there, and thanks for the great job you re doing here.
my concern is about use of Builder :: elemMatch in the select part of the query builder,
the available elemMatch method of query builder is now usable only as part of query part not the projection one.

would it be possible to add something like selectSlice to do so :

public function selectElemMatch($fieldName, $elemMatch)
{

    $this->query['select'][$fieldName] = array($this->cmd . 'elemMatch' => $elemMatch);
    return $this;
}

or simply modify the select method to with a second argument (defaults to 1), to hold the elemMatch filter condition.

Regards