Issue 4044: Search overhaul, part 1

Issue 4044: Search overhaul, part 1

This is just the json generation and indexing bits to send data to the new Elasticsearch cluster, with rake tasks to do a full reindex. We still need to hook it into the callbacks -> redis buffer cycle and create the new search classes. 

https://code.google.com/p/otwarchive/issues/detail?id=4044
It doesn't seem likely to me, and the idea was to have consistent attributes across bookmarkable types - works and external works both have a single language_id field. But it does seem kind of non-ideal, and hence the fixme comment.