CAS-1480: Moving proxy authz over to httpBasedHandler

`HttpCredential` is now keeping track of the actual service and will be able to determine if proxying is allowed. 
I'd love to, but in this case, there aren't any particular fields to evaluate. Just a few standard rules, recommended by the javadocs of the EqualsBuilder itself:
http://commons.apache.org/proper/commons-lang/apidocs/org/apache/commons/lang3/builder/EqualsBuilder.html