add handleActions redux util

ui/js/util/redux-utils.js

@@ -0,0 +1,10 @@
+// util for creating reducers
+// based off of redux-actions
+// https://redux-actions.js.org/docs/api/handleAction.html#handleactions
+export const handleActions = (actionMap, defaultState) => {
+  return (state = defaultState, action) => {
+    const handler = actionMap[action.type];
+    const newState = handler ? handler(state, action) : {};
+    return Object.assign({}, state, newState);
+  };
+};