deposit: separation of conferences typeahead

* Generalises extended typeahead to be used for other things not
  only conferences.

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>
deposit: conferences typeahead

* Removes id from cachedQuery. This prevents reset to that string on
  backspace/delete after the page refresh.

Signed-off-by: Kamil Neczaj <kamil.neczaj@cern.ch>