add selection type (#1944)
add selection type (#1944)

* add selection type

* add multi selection property to match with apps/prepopulate/data_init/vocabularies.json
superdesk/superdesk-core,petrjasek/superdesk-core,superdesk/superdesk-core,petrjasek/superdesk-core,petrjasek/superdesk-core,superdesk/superdesk-core,superdesk/superdesk-core,petrjasek/superdesk-core