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.

Ok I see, the SecurityAuthenticationHttpHandler takes in the CConfiguration object.  But since we're reading securityEnabled and realm in the coopr code and passing it into the SecurityAuthenticationHttpHandler, at least those 2 config settings can come from coopr specific setting names instead of cdap setting names.  @sreevatsanraman we should be sure to remove usage of the config when extracting that class into the common repo