Re-added author, subject and title spellcheckers (copied from blacklight-jetty)

Blacklight generator adds search fields to catalog controller that expect spellcheckers, e.g.:

    field.solr_parameters = { :'spellcheck.dictionary' => 'title' }

The author, title and subject spellcheckers were previously in the hydra-jetty solrconfig.xml, but were removed for some reason.