Refactor of DataListToolbar. Creates a number of smaller components used by the toolbar. Adds support for passing in an add button node to the toolbar.

__tests__/components/ExpandCollapse.test.jsx

@@ -0,0 +1,23 @@
+import React from 'react';
+import { mount } from 'enzyme';
+import { I18nProvider } from '@lingui/react';
+import ExpandCollapse from '../../src/components/ExpandCollapse';
+
+describe('<ExpandCollapse />', () => {
+  const onCompact = jest.fn();
+  const onExpand = jest.fn();
+  const isCompact = false;
+  test('initially renders without crashing', () => {
+    const wrapper = mount(
+      <I18nProvider>
+        <ExpandCollapse
+          onCompact={onCompact}
+          onExpand={onExpand}
+          isCompact={isCompact}
+        />
+      </I18nProvider>
+    );
+    expect(wrapper.length).toBe(1);
+    wrapper.unmount();
+  });
+});