New DUB documentation

[WebFreak001]

the revamped DUB documentation I started a while ago is now 
deployed on https://dub.pm

A bunch of pages are still WIP, but the already done pages have a 
bunch of new information and should be better structured. I 
recommend giving the new documentation a try, maybe you will 
learn something new about DUB.

If you find anything to edit, the "Edit this Page" button makes 
it trivially easy - it's all standard markdown files now that are 
easily editable.

If you previously often looked at the recipe page that contained 
all the information in a single page, you will find most of the 
information on https://dub.pm/dub-reference/build_settings/ now 
and there are even more details on separate pages now.

The site's built-in search on the page works great and runs fully 
offline, try it out! It will find your search across the entire 
documentation. CLI documentation is now also included more 
similar to the man page format here.