New paths to set redirect URL in session and perform redirect
Perform redirect, setting window.opener to null.

This will prevent the linked page performing any action on the original
window.
New function to set linked URL in session and perform redirect.

This replaces the function which set '_blank' on all external URLs.
Added an account page setting "Open forum links in new window"
Add explicit link target rather than noblank class.
Rewrite href to redirect URL on click for external links.

This redirect requires the CSRF token so you can't build arbitrary URLs.
Updating markup test for new window URLs
Simplified mousedown handler for anchors
Don't set redir URL as last in session.

We don't want to redirect to external links (or a crash page!) on login.
Merge branch 'external-link-redirector' of https://github.com/jbarrett/community-platform into jbarrett-external-link-redirector

Conflicts:
	lib/DDGC/DB/Result/User.pm
Merge branch 'jbarrett-external-link-redirector'