Feature/auth service integration

Integration of COOPR server and External Authentication service from CDAP project. As was discussed before with @sreevatsanraman , I used dependency to the cdap repo, but in future it should be replaced with dependency to the common repo. 
Also, I copied class ```SecurityAuthenticationHttpHandler``` from the ```cdap-gateway``` package. This class also could be reused, so @sreevatsanraman , could you please move this class to the common auth service too? Then we could delete it from this repo. 
@albertshau , please take to review this PR.

I think, that configuration classes will be moved to the common repo with auth service. Yes, this class, by default, loads cdap configs, because they are hard coded there, as you could see. I don't like this, the same, as you, but, unfortunately, auth service is using this class now. Hope, after refactoring and moving auth client to the common repo, this could be changed too.