App now better understands SSL

Still a long way from finished, but now analytics (Omniture) understands http and https

Images now understand https

During local development the nginx will now forward the X-Forwarded-Proto header like an ELB does
mERGE BRAnch 'master' of github.com:guardian/frontend into ssl-preview
Merge branch 'master' of github.com:guardian/frontend into ssl-preview
tab - spaces - tab - spaces
seriously
Merge pull request #5601 from guardian/ssl-preview

App now better understands SSL