[Request] Saving to a currently-occupied slot clears out the old image first

[cviebrock]

Right now, it just throws an SQL error: Integrity constraint violation: 1062 Duplicate entry ....

My repo code currently looks like this:

// clear existing first from the slot
if ($slot) {
    Imager::deleteBySlot($slot, $post);
}

// save new
$image = Imager::saveFromFile($file, $post, $attributes);

Just being able to saveFromFile and letting the package handle this for me would be cool.