Extended AuthDto with Info parameter so clients can query Session status

I propose this change to allow clients like Single Page Application to query session status by making requests like `http://localhost:38866/auth.json?info=CurrentSession`

For example, in my angularjs SPA application I have controller which swaps "sign in|sign out" links in header menu. Since this is SPA and I it requests it's data in small chunks and present received data with appropriate templates. 

I could use $watch and listen to changes in my utmUserAuth service (a service as in angular domain) and set/reset session on login/logout by using the session information returned, but then I have to figure out how to handle oAuth logins, which just redirect to "success" url without providing explicit session details.

To workaround this, I had to create new DTO (thus minus one useful DTO on my "free-loader-license" :smile: ) VerifyAuth and assigned it to route "/auth/verify". 

The snippet bellow shows my workaround (commented out) and the use of the proposed change.

    angular.module('app.controllers', [])
    .controller('SiteHeaderController', [
        '$scope', '$http', '$location', 'utmUserAuth', function($scope, $http, $location, utmUserAuth) {
            $scope.isAuthenticated = false;
            $scope.userName = '';
 
            //// Old code uses custom VerifyAuth Dto with route "/auth/verify"
            //
            // $http.get($scope.apiPathPrefix + '/auth/verify.json')
            //     .success(function(data, status, headers, config){
            //         utmUserAuth.setSession(data.sessionId, data.userId, data.userName);
            //         $scope.userName = data.userName;
            //         $scope.isAuthenticated = true;
            //     })
            //     .error(function(data, status, headers, config){
            //         utmUserAuth.resetSession();
            //         $scope.isAuthenticated = false;
            //     })
 
            $http.get($scope.apiPathPrefix + '/auth.json?info=CurrentSession')
                .success(function(data, status, headers, config){
                    if(data.userId !== undefined) {
                        utmUserAuth.setSession(data.sessionId, data.userId, data.userName);
                        $scope.userName = data.userName;
                        $scope.isAuthenticated = true;
                    } else {
                        utmUserAuth.resetSession();
                        $scope.isAuthenticated = false;
                    }
                })          
        }
    ])

and here is an animated screencapture of the result in action:
![header](https://cloud.githubusercontent.com/assets/204439/2994489/2601c6ea-dcce-11e3-920e-d75feb048e44.gif)

Kind regards,
Rouslan Grabar