dynamic callback urls

Hi, I made some changes mainly to pac4j-core and pac4j-cas to support non absolute callback urls. I have a situation where my application can be served up through multiple domains (whitelabeling). So, for example, I can access my application by going to brand1.com or brand2.com. So I want to be able to dynamically set the CAS login and callback urls based on whatever the current host/domain is. Let me know if there are any revisions you want done to these first and I'll make them asap.