CAS-1474: Deprecated unneeded "requireSecure" settings 

The `requireSecure` property is no longer needed, as the security enforcement of callback urls should be handled by the proxy settings of a given app. 
I am less concerned about breaking API changes, seeing that we are protected by the release strategy. This is not to say that we should be careless of course, and Scott has reminded me to take an effort to deprecate APIs where we can and that's certainly warranted. Sometimes, we cant help it. If we were shooting for a 4.0.1 I would have certainly taken on a way more modest approach.