[ADF-814] application configuration service (#1969)

* app configuration service

* api improvements and readme update

* extend readme and add defaults

* unit tests for app config service

demo-shell-ng2/config/webpack.common.js

@@ -101,6 +101,9 @@ module.exports = {
                 from: '**/*.json',
                 to: 'resources/i18n'
             },
+            {
+                from: 'app.config.json'
+            },
             {
                 from: 'favicon-96x96.png'
             },