Add model and endpoint for settings js

[mwvolo]

Exposes settings for os-webview settings.js file

Endpoint: /apps/cms/api/webview-settings

Example output:

{
  "settings": [
    {
      "name": "analyticsID",
      "value": "UA-73668038-1"
    },
    {
      "name": "analyticsID2",
      "value": "UA-73668038-2"
    }
  ]
}