Use types in elasticsearch for differend haystack indexes.

Fixes #503, thanks to @davedash for previous patch on which this one is
based.
The ignore=404 on line 236 does double duty I think. It gets us past the doc_type not existing as well as the index. However if the index doesn't exist line 240 will throw a 404 and fail an index rebuild. I gather your intention is to ignore the index missing here as well per this commit - https://github.com/toastdriven/django-haystack/commit/2b2b434998002abb8e804e34fa22a1777d99653f