Automatically close unclosed HTML tags.

Fixes an old problem with some unclosed <b> or <div> messing up
the layout of docs.

In addition to automatically closing the tags, a warning gets printed.
Extract HtmlStack class from DocFormatter.
Implement --ignore-html option.

Allows for ignoring additional HTML tags which otherwise would get
closed down by the new automatic tag closing mechanism.

Useful for ignoring ExtJS preprocessor directives: <debug>, <locale>.
Fix HtmlStack#open? method.

A silly mistake.
Improve wording of 404 page.

Don't direct people right away to JSDuck issue tracker - most likely
it's just a fault of a broken link and it's the authors of the
documentation who should fix it.
Display title text on loading screen.

Instead of using hardcoded image with text "Sencha Docs".
Default to Object when no type specified by @return.

This fixes the issue of return value docs being completely missing
in case @return wasn't followed by {TypeDef}.
Remove WebKit restriction from --touch-examples-ui.

No more does using this option restrict viewing of inline examples
to WebKit based browsers.  This check is now moved over to
eg-iframe.html in Sencha Touch codebase.