Update Logout procedure

[srkirkland]

When doing a logout or endEmulate, we want to kill the Harvest auth cookie but not redirect to CAS. Will require making an anonymous page where we can redirect to.

CAS would prefer if you don't do a full SSO logout with your app logout. Plus it'll make emulation 1% faster.

[srkirkland]

Details: clicking the logout button fires a POST to the account/logout endpoint, which is in the AccountController.cs. Right now it does a signout and redirects to an external signout page. Here are the steps that it'll take to fix this issue:

• Put the [HttpPost] attribute on the logout method so it only responds to POST
• remove the external redirect and instead just return a view return View().
• Create a new view which has some simple banner text saying "You have successfully been logged out". Look at the current accessDenied.cshtml view from the same controller for an example.

@mxthu313 ☝️