Have been retired and made into something better. Use Report Displayers instead.
See /embedding/apps-a or Apps/C Grunt Build. The changes are as follows:
Widget becomes an App.
The main class in presenter.[js|ts|ls|coffee] has been changed from Widget to App.
A config file with dependencies for a particular App is moved to its folder in the form of a config.js file. The contents of this file is being exported and contains example config to be passed from middleware and/or client.
The Java service serving Report Widgets has been retired from InterMine core.
The Node.js service now works as a middleware. You can plug it into your (Node.js) app by passing an array of paths on local or remote systems where it can find the App sources.