Add `OAuthScope` getter/setter to the RedirectLoginService.
This change allows specifying the 'scope' parameter when requesting an
authorization code & token.
This is necessary if using an OAuth client that doesn't allow requesting
tokens with the default 'user:full' scope.
e.g. A ServiceAccount OAuth Client https://docs.openshift.com/container-platform/3.6/architecture/additional_concepts/authentication.html#service-accounts-as-oauth-clients

*Example Usage*

```js
angular
  .module('myApp', [
    'openshiftCommonServices'
  ])
  .config(['RedirectLoginServiceProvider', function (RedirectLoginServiceProvider) {
      RedirectLoginServiceProvider.OAuthScope('user:info user:check-access');
  }])
```