[AH-62] Add "Not found page" (404) for unsupported routes

[Shagon1k]

e.g. http://localhost:1337/asd

"Page not found. Go to Main Page" - use "steampunk thematic" text.

"This is not the page you're looking for." and Yoda steampunk

Update "steampunk thematic" text for page under construction.

[Shagon1k]