elinks.conf: Don't let elinks change my config

* Use extended regex search by default
* Fix quvi arguments order
* Switch to `sxiv` for images
* Tidy up a bit
launchv.js: Prefer `yt-dl` over `quvi`

youtube-dl has for a long time supported more than quvi and while quvi
can be faster when extracting the uri, youtube-dl actually works.