Add HTML 404 File

[Digi59404]

Google/Bing place very high priority on sane 404 pages. Not to mention from a marketing standpoint a sane 404 page can make the difference between leaving a website and being sucked into another article.

This PR allows for a basic 404.html file to be used - Ideally a 404 Controller should exist for dynamics and fun. But for right now - this will work.

Give users a pretty 404 page instead of a blank page.

[nmelnick]

Thanks for the contribution! Admittedly, I think I just expected the front web server to handle the 404 and show another page, but this is great for an enclosed environment or against a server that won't do it.

[Digi59404]

Welcome! More will be coming! I have a bunch more to add.

I run ambition in front of Nginx - But I know for numerous enterprise and marketing reasons companies and groups like to have their own 404's.