PLT-2600/PLT-2770 Added Get Public Link modal and added new API for public file links (#2892)

* Switched public file links to use a GetLinkModal

* Separated getFile and the new getPublicFile api calls

webapp/stores/modal_store.jsx

@@ -37,6 +37,7 @@ class ModalStoreClass extends EventEmitter {
         case ActionTypes.TOGGLE_GET_POST_LINK_MODAL:
         case ActionTypes.TOGGLE_GET_TEAM_INVITE_LINK_MODAL:
         case ActionTypes.TOGGLE_REGISTER_APP_MODAL:
+        case ActionTypes.TOGGLE_GET_PUBLIC_LINK_MODAL:
             this.emit(type, value, args);
             break;
         }