fix measurement gist issues with better state management

sites/shared/hooks/useGist.js

@@ -0,0 +1,36 @@
+import useLocalStorage from './useLocalStorage';
+import set from 'lodash.set'
+import unset from 'lodash.unset'
+import defaultSettings from 'shared/components/workbench/default-settings.js'
+
+// Generates a default design gist to start from
+const defaultGist = (design, locale='en') => {
+  const gist = {
+  design: design.config.name,
+  version: design.config.version,
+  ...defaultSettings,
+  _state: {view: 'measurements'}
+  }
+  if (locale) gist.locale = locale
+
+  return gist
+}
+
+function reducer(gistState, {path, value, type='set'}) {
+	const newGist = {... gistState};
+
+	switch(type) {
+		case 'replace' :
+			return value;
+		case 'unset' :
+			unset(newGist, path);
+			break;
+		default:
+			set(newGist, path, value);
+	}
+	return newGist;
+}
+
+export function useGist(design, app) {
+	return useLocalStorage(`${design.config.name}_gist`, defaultGist(design, app.locale), reducer);
+}