Introduce IP parameter to IdAPI register call

This gets populated by the remote address from Play, which will use
X-Forwarded-For or the remote address as appropriate.
Introduce RemoteAddress trait
Update ID custom IP header name
Add HeaderLoggingFilter to Identity

Allows us to log request headers for debugging (e.g. for geolocation
testing).
Merge pull request #1667 from guardian/add-geolocation-to-idapi-registration-calls

Add geolocation to idapi registration calls