LPS-42060 - Add visual grouping of repeatable fields in the Dynamic Data Display.

Hey @natecavanaugh,

Attached is an update for http://issues.liferay.com/browse/LPS-42060.

NOTE: These styles are copies from the web content display portlet (https://github.com/liferay/liferay-portal/blob/master/portal-web/docroot/html/portlet/journal/css/main.css#L144-159)

Please let me know if you have any questions.  Thanks!