Including images from the 'static' dir to a CLI generated Webpack project results in duplication in output bundle

**I'm submitting a bug report**
Here is another issue with the CLI generated webpack config that soon becomes apparent once an app starts to be built.

* **Loader/bundler:**
Webpack

**Current behavior:**
If you go down the logical steps needed to include an image in your app, ie. add an image inside 'static/images' dir then add the image to your html file like this:
```

Start in the CLI-generated webpack configuration at the CopyWebpackPlugin entry shown in the issue, then build a project containing an image under static/images and inspect dist. The work is done when referenced images are emitted once while the unreferenced favicon remains available in the output.

Written by the indexing model from the issue text.