Restrict access to ui from non whitelisted IPs

[vohmar]

Currently we restrict access to the portal post authentication. So anyone can get to the portal and start authenticating.

Lets bring the limitation a step ahead and limit access to the ui anyone coming from non-whitelisted IP. So each user trying to get access to the portal ui needs to come from only whitelisted domains - before returning user the option to authenticate the ip should be checked against the full list of allowed IP addresses. If IP is present then login screen is returned, if missing then errror is returne indicating that user is not allowed to access this page/service