Tabs patch!

CHANGES
-------

 + Introduced tabs. First, we extended the menu system to support tabs. Next, a tab was added for every link that was (1) an administrative action other than the implicit 'view' (2) relevant to that particular page only. This is illustrated by the fact that all tabs are verbs and that clicking a page's tab leads you to a subpage of that page.

 + Flattened the administration menu. The tabs helped simplify the navigation menu as I could separate 'actions' from 'navigation'. In addition, I removed the 'administer > configuration'-menu, renamed 'blocks' to 'sidebars' which I hope is a bit more descriptive, and made a couple more changes. Earlier, we already renamed 'taxonomy' to 'categorization' and we move 'statistics' under 'logs'.

 + Grouped settings. All settings have been grouped under 'administer > settings'.

TODO
----

 + Update core themes: only Xtemplate default supports tabs and even those look ugly.  Need help.

 + Update contributed modules.  The menu() hook changed drastically.  Updating your code adhere the new menu() function should be 90% of the work.  Moreover, ensure that your modue's admin links are still valid and that URLs to node get updated to the new scheme ('node/view/x' -> 'node/x').

- Partial patch #8284 by jseng: made the RSS auto-discovery URL absolute even though that is not strictly necessary.

- Patch #8553 by Moshe: hide the 'add new comment' link when showing the
  comment form.

- Patch #8405 by Adrian:
   + Fixed duplicated view.
   + Fixed node types not being picked up correctly.
   + Improved error handling in case a particular node has not been found.

- Patch #8477 by Goba: fixes issues of newline handling in filters, unifying what newline should a filter expect, and fixes the missing title filter tip issue.

- Patch #8357 by Ax: added support for mt.getRecentPostTitles to the
  blogapi module.  Used by ecto.  I changed '$titles_only' to '$bodies'
  as the patch favored '!$titles_only'.

added double-width dot and comma, and right-to-left question mark as sentence boundaries.

- Fixing a copy paste error in file.inc.
- Some double => single quote changes.

- Patch #7350 by Mathias: return part a taxonomy tree to a user-defined
  depth/level.

- Updated CHANGELOG.txt.

- Reworked comment submission.  It is less broken now.

- Updated the form handling to use form_set_error().  All core modules have
  been updated (almost none have error checking for forms) except the node
  forms ...

- Improved form handling.

  + Introduced two new functions:
      1. form_set_error($name, $message): files an error against the form
         element with the specified  $name.
      2. form_has_errors(): returns true if errors has been filed against
         form elements.

  + Updated the form handling:
       1. The form_ functions will add 'class="error"' when a form field
          has been found to be erroneous.
       2. The error message is passed to theme_form_element() when the
          particular form field has been found to be erroneous.

  + I updated the user and profile module to take advantage of these new
    functions.

  + IMPORTANT: the _user() hook changed.  The 'validate' case should no
    longer retun an error message when something goes wrong but should
    set it with form_set_error().

- Fixed empty searches being logged.
- Trim whitespace from start and end of search key.

- Patch #6863 by Moshe: add 'class="active"' to the table elements of
  the active column.

- Patch 7444 (#35) by Pablo.  This patch addresses some issues with showing
  anonymous usernames in comments.  It does not solve all my problems, but
  others claim it works as advertised.  I'm committing this because it does
  fix some pending issues (even though that might not be the end of it).