Enhanced Layer List - Metadata Dialogs (Tested up to WAB 2.15)
Update July 2017: adds REST Link and 'No Information Available' features.
Update December 2019: Still works great in current WAB (use the code here but insert it in to a current version of the widget.js in the existing 2.14 WAB)
GitHub Link: GitHub - kevinsagis/EnhancedLayerList
You can see this widget in action at SAGIS Property Map Viewer
Enhanced Layer List adds metadata Dojo dialogs to display the Description and Copyright text fields from the REST service. This replaces the standard out-of-the-box function that opens a new tab or window to display the Esri REST Service page when a user clicks the "Description" item in the '...' menu on a layer in the Layer List widget, and displays these dialogs instead. This is more friendly to the end user. Also includes LayerListView.js autoexpand mod for the layerlist based on posts from Robert Scheitlin et al in https://community.esri.com/thread/160914
Files that were modified are in widgets\eLayerList\PopupMenu.js and PopupMenuInfo.js
It only displays Copyright if it's present. Same for Description. It won't display a Dialog if there is no description, such as for Group layer IDs.