Improves the loopback auth. handling in working

Fixes a problem with the handling of IPv6 when checking for loopback
requests in ViewPage.action.

Adds a check for the header X-Forward-For when checking for loopback
requests in ViewPage.action.
Merge pull request #8 from stenbacka/viewpage-loopback-check-with-proxies

Improves the loopback auth. handling in working