Revert "Change login/createaccount forms to new appearance"

The code did not go through a proper review process, and - quite
simply - it is unacceptable by core standards (or by any standards, to
be honest).

* It "[u]ses JavaScript to munge the create account CAPTCHA", to quote
  the commit message
* It is littered with TODOs and FIXMEs, as well as messages from one
  coder to the other and commented-out code
* It modifies some HTTPS-related logic for no obvious reason (it's not
  documented or even mentioned *at all* in a otherwise front-end
  changeset)
* It happily disregards code conventions (trailing spaces, #-comments,
  CSS formatting)
* It includes different CSS font-family rules that the entire rest of
  software uses for display, creating design inconsistency
* It hardcodes links in the format "/wiki/XXX"
* It hardcodes English-language link hrefs

This reverts commit 92bb00d35688e72ebeea75ed55a6db981cfb71e5

Conflicts:

	languages/messages/MessagesEn.php

Change-Id: I00d72fe157e697d5cf926e75bcea5db0bee153e5