deposit: separation of typeahead initialization

* Separates connecting events and initializing typeahead so that
  one can set up a custom typeahead with all the events connected
  with the form.

Co-authored-by: Kamil Neczaj <kamil.neczaj@cern.ch>
Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>