After login, redirect the user to the previous page they were on

- Added a config option to toggle the behavior
- Auto-detects the last page they visited, stores it in a session variable
- Hooks into MvcEvent's onFinish event to retrieve the content-type from the response to ignore non-html pages so we can prevent AJAX requests from being set as the return target
- Override from query string supported so an application can support fragments in URLs if necessary
- Query string strips out base URLs so malicious users can't use your application's URL to redirect people to somewhere off-site