LPS-46696 - Prevent unintentional portlet dragging on mobile devices

Hi Jon,

Attached is an update for https://issues.liferay.com/browse/LPS-46696.

Based on Nate's recommendations in https://github.com/natecavanaugh/liferay-portal/pull/2472, I am now setting the handles in bottom_js.jspf to just the portlet-title-text if the user is mobile.

Also, since Drag expects an array of strings for the handle/s, I added a check in layout.js so that Liferay.Data.PORTLET_TOUCH_DAG_HANDLE_SELECTOR can be set to a string or an array of strings.

Please let me know your thoughts.

Thanks!