[O] Request: Move org-eww from contrib to core

[Matt Lundin]

Given that the coming release of emacs 25 ships with the eww browser, I
think it would be worthwhile to make org-eww.el a core org-mode module.
I have been using eww instead of emacs-w3m for some time now with no
problems. Since org ships with support for emacs-w3m, an external
package, it seems to makes sense also to support eww, the built-in
browser.

I noticed that Marco Wahl, the author of org-eww.el, is on the
contributors list, so, if I understand correctly, there shouldn't be
copyright issues.

Matt