RememberMeManager should have access to Subject context map

A bug surfacing in the ShiroFilter showed that WebUtils.bind* methods needed to be called before the WebSubject.Builder could be used. This is because the RememberMeManager does not accept a Subject context map from where it could receive the Request and Response objects, so it must look them up from the thread, which surfaces the fragility of assumptions made about the thread.

Instead, the subject creation context map should be given to the RememberMeManager so it can use whatever it needs inside the map to use to lookup the identity if necessary.

See http://www.mail-archive.com/shiro-dev@incubator.apache.org/msg00178.html for details.