Remove _blank and _new targets from links

_blank with #anchors triggers a bug in [Firefox](https://bugzilla.mozilla.org/show_bug.cgi?id=668213)

_blank and _new are 1990 patterns that are [discouraged today](http://www.nngroup.com/articles/the-top-ten-web-design-mistakes-of-1999/).

If the users want to open a new window, they will right-click/open in new tab, shift-click or middle click the link. That is what they do in all other websites already.