feat(registries): add registry management (#930)

app/helpers/registryHelper.js

@@ -0,0 +1,18 @@
+angular.module('portainer.helpers')
+.factory('RegistryHelper', [function RegistryHelperFactory() {
+  'use strict';
+
+  var helper = {};
+
+  helper.getRegistryByURL = function(registries, url) {
+    for (var i = 0; i < registries.length; i++) {
+      if (registries[i].URL === url) {
+        return registries[i];
+      }
+    }
+
+    return null;
+  };
+  
+  return helper;
+}]);