mixer: license KB update

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>
deposit: remove file sortable option

Signed-off-by: Javier Martin Montull <javier.martin.montull@cern.ch>
deposit: conference typeahead improvements

* Removes reverting the cached value on backspace key.

* Hides warning message when the conference field is empty.

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