API cleanups, break 1.x API

First, this patch includes the #406192 patch to avoid duplicate effort.

The processor hook operations have a unified form:
hook_feedapi_item($feed_nid, $item = NULL, $settings = NULL);
'fetch' op is removed. it was not used.
'save' was renamed to 'insert'. It's because we also have 'update' and now it's more straightforward.

WARNING: This patch breaks the API. If it will be committed, this means a new branch, 6.2.x