Added goto-trigger hooks, testlinks plugin

Now it is possible to form your own RSS feed based on links you read.

Maybe I'll add more hooks and plugins someday, for example I am intended to write rss feed generator based on these hooks.
Also, I did not named these hooks as "curses-*". If you want to keep all canto-curses hooks name as "curses-" and all canto-next hooks as "next-", I can quickly amend this commit with new hooks names.