Include parser result in hook_feeds_presave

Issue Summary

Problem/Motivation

There are several use cases where the need arises to alter an imported entity based on the parser result.

HOOK_feeds_presave is great for doing alterations, but parser results are not passed down to this hook.

Proposed resolution

Make the FeedsParserResult $item the third argument for HOOK_feeds_presave().

The signature would change to function hook_feeds_presave(FeedsSource $source, $entity, $parser_item)
I would feel more "right" to me to have $item be argument number 2,
but by adding it as third bakckwards compatability is guaranteed, no one needs to alter the hook.

I will attach a patch soon.