Unlike the old one which was called $heading, this one is in caps to be
more distinctive when it's assigned. It's also NOT html escaped, so any
assigns to it should escape their value.

The old theme_setup() supported them, so now we do too.

* The old searchform() calls have been removed and now instead a smarty
  function has been registered called user_search_form that is used to
  display it - no more assigning searchform() in php files.
* assign calls for 'heading' have been removed as they're now useless
* The language selector is now displayed on all logged out pages that
  don't define 'nosearch' - just like the user search form

The old functions will still work, at least for 1.2. We'll probably
remove them in a future version, 1.3 or later.

The smarty function has been replaced and the old one deprecated, as the
old one had a misleading name and slightly annoying calling convention.

So far only stuff in lib/web.php and a couple of other places have been
switched.

Now the table for the user search form/language selector is gone. Other
HTML has been cleaned up too.

The magic of the CSS means that the main content column is always first.
No tables in sight!

Sets defaults for other themes.

Reads in themeconfig.php for all themes. Allows the theme objects to set
their own fields if necessary.

The root theme is now 'raw', and this cannot be changed. All themes
extend from the raw theme.

A bunch of fields were added to do with the widths and colours of the
columns. Now, it's technically possible for a Mahara site to have
sideblocks on the left, or sideblocks on both sides, and the widths of
these columns can be set in pixels or percent.

Also make sure that form never steals focus, and remove a dead line.

It's broken because it corresponds to the theme of the site, rather than
the theme the user is looking at the site with. I don't think this ever
resulted in any broken images however.

Most annoying on public pages where the login box is shown. When it gets
the focus it scrolls the document there which is annoying when you were
reading something below the fold, like a forum post.

This matches langconfig.php for the language files.