Fix Documentation page titles (OUR-31)

Sets the `<title>` tag for Documentation pages.

The macro `Title.xslt` has a placeholder for a HTTP item called `topicTitle` - which I hijack in the `SearchForMarkdown` (NotFoundHandler) class - setting the value of the page title.

The format of the page title is a reverse-breadcrumb e.g.

```
Content - uQuery - Querying - Reference - Documentation - our.umbraco.org
```

The 2nd changeset is some minor config/XSLT tidy-up.