Make directive to accept onScan and beforeScan callbacks instead of broadcasting 'dataScanned' event.

This will allow to reuse directive for screens different from 'send'

src/js/controllers/topbar.js

@@ -1,6 +1,14 @@
 'use strict';
 
-angular.module('copayApp.controllers').controller('topbarController', function($rootScope, $scope, $timeout, $modal, isCordova, isMobile, go) {   
+angular.module('copayApp.controllers').controller('topbarController', function($rootScope, go) {
+
+  this.onQrCodeScanned = function(data) {
+    $rootScope.$emit('dataScanned', data);
+  };
+
+  this.openSendScreen = function() {
+    go.send();
+  };
 
   this.goHome = function() {
     go.walletHome();