[1.0.X] Auth-related doc cleanups:

  * Added to documentation of missing characters from `allowed_chars` in `make_random_password`.
  * Fixed several long lines and word wraps.
  * Added a reference link to the "How to log a user in" section and made a later reference to this section an actual link using the `:ref:` directive.
  * Turned a command line code example into a code block.
  * Added attribute reference link for a ``request.META`` mention.
  * Added `code-block:: html` directives for HTML examples.
  * Corrected reference links for all the `auth.views` functions.
  * Added a few function signatures and documentation of optional parameters that were missing for some of the the `auth.views` functions (refs #10272).

Backport of r9835 from trunk.


git-svn-id: http://code.djangoproject.com/svn/django/branches/releases/1.0.X@9836 bcc190cf-cafb-0310-a4f2-bffc1f526a37