Add support for cshs module

First of all thanks a lot for writing this awesome module! This improves the authoring UX by a great margin.

Problem/Motivation

I've recently used a module to improve UX of term reference widget, cshs. None of the logic in label_help_form_alter addresses the form array used in cshs widget, i.e. $form[$key][$item['#language']][0]['tid'].

Proposed resolution

The patch in the comment below.

Remaining tasks

For @sheldon-rampton to validate the patch and merge.