User current app type should be recorded specific to the server (host name) accessed

[philayres]

On systems that share a database for users, but run different apps, recording the app_type_id for the user causes issues, since the last app type selected on another server will not really apply across all servers that use the ml_app.users table. This causes confusion on later logins, and the inability for a user logged in on one server to use a different app when logged in on another server.

We need to find a way to handle this, without having to address every piece of code that looks at he current user app_type / app_type_id.

[philayres]

Alternatively, have each request indicate the current app type id using a request header or meta tag, or namespacing the url