Interface:
* Restore sitename as part of error page document title
(follows-up 4ca9805). Moved to general Exception class as it
is useful in general, this effectively changes the title from
"This wiki has a problem" to "Internal error - Wikipedia".
* Added basic <style> to have it use a sans-serif font and a bit
padding to offset it from the edge of the window.
* Output stacktrace in <pre> as-is (with linebreaks) instead of
in a <p> with <br/>.
Clean up:
* Removed spurious "<!-- SiteSearch Google -->" comment.
* Change sitesearch radio button to not need the id/for
attributes but simply nest them. Visual rendering and browser
behaviour is identical.
* Renamed $text to $html since that is what it is (follows-up
4ca9805 which reused that variable for html, it used to contain
text).
* Remove odd linebreak from "dberr-problems" message, it was
being output as-is in the html (html escaped, of course) and
line breaks have no meaning inside an <h1> tag. Using a simple
space instead. Visual rendering is identical.
Coding style:
* Using <!DOCTYPE html> instead of <!doctype html> for consistency
with other documents we output.
* Switched a few inline #-style comments to use // instead.
* Switched a few strings from double quotes to single quotes in
areas close to the changed code.
Change-Id: I33232d871200cbd23501c9a6c5f8a178931e135e
2bcffe8be4