deposit: duplicate validator with prod inspirehep

* Queries inspirehep.net to check if a submited publication is
  already in the production db.

* Introduces PRODUCTION_MODE variable which enables cooperation with
  inspirehep.net server.

* NOTE Set PRODUCTION_MODE=True in your config to use the validator.

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

* Autocomplete fetching starts after 3 characters.

* Passes all items from ajax request up to 100.

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

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

* Fixes value reset on blur.

* Fixes  undefined value errors on keypress after a suggestion was
  chosen and the user exited the input field.

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

* Syncronizes value of the hidden conference_id field with the id
  from conferences field.

* Adds SychronizedField class which can be reused to do this.

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

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