Don't show the user the path files temporarily downloaded by WebEnginePart

When clicking on a remote URL from within WebEnginePart, if the URL must be shown in a different part, it is downloaded to a temporary file. The path of this file was shown in several places (location bar, title bar, ...) and also ended up in history and in session files. Besides exposing to the user what is an implementation detail, it caused problems with session management, since when Konqueror exits, the temporary files are deleted and aren't downloaded again when the session is loaded.

To avoid all of this, now KonqView has two different concept of URL: the logical URL, which is exposed to the rest of the application and to the user, and the real URL which can be the URL of the temporary file and it's only known to the view.