publicPath options differs from traditional publicPath options

[TerryRPatterson]

Normally the 'publicPath' denotes the URL where assets are hosted if the URL is different from the main HTML page.

I suggest that we either remove the publicPath from the file system path, or add a new option that affect the exports URL, but not the file system path; maybe called hostingPath.

I think the change to publicPath would be a better approach long term, but it is a breaking change.