Autoredirect if referer origins from same domain

This fixes https://github.com/owncloud/mail/issues/179
Remove uneeded import
Show a spinner in case JS is not yet properly loaded
Open links in new tab
improve styling for link redirect page
make redirect page work on mobile as well (remove wrapping divs + indentation change)
try to make redirect work again
close the session in the proxy controller - enables parallel download
fixing auto redirect
Merge pull request #192 from owncloud/show-no-referrer-warning

Autoredirect if referer origins from same domain