search: loading of Bloodhound using requirejs

Twitter's typeahead exports also Bloodhound their data fetching engine. It is a missing part of the current configuration. However everything works in the current pu because loading of 'typeahead' dependency stores `Bloodhound` class in the global namespace anyway. This PR makes possible loading Bloodhound in a proper requirejs way.

I haven't modify here the deposit module because it uses custom data fetching.
like https://github.com/inveniosoftware/invenio/pull/2277/files#r17476304