Fix lodash ES module imports

[nikku]

Bundling the library with browserify / babelify yields the following output:

[BABEL] Note: The code generator has deoptimised the styling of "{PROJECT_DIR}/node_modules/dmn-js-properties-panel/node_modules/lodash/lodash.js" as it exceeds the max of "500KB".

It hints us on the fact that the full distribution of lodash (> 500KB) is being packed into the properties panel.

To properly consume lodash so that ES module aware bundlers can tree-shake it we must not use destructuring syntax:

import { forEach, map } from 'lodash';

Instead, we must import individual utilities like this:

import forEach from 'lodash/forEach';
import map from 'lodash/map';

The alternative is to use lodash-es. However, that library variant has tree-shaking issues, too (as far as I am aware).