support for "minDubVersion" recipe entry

[rtbo]

Not all recipes may work with old dub versions. see #1450 or #1453.
Specifying the minimum required dub version in the json/sdl file allows meaningful error message instead of a build error the user would be unable to understand.

[dhasenan]

More ideally, dub would use semantic versioning for things like this, and dub.json would allow you to rely on a range of dub versions. Then dub would automatically download a compatible version of itself, just like regular dependencies, and invoke that.

That's a much bigger change, but we can at least lay the groundwork by using "dubVersion": "~>1.11.0" instead of "minDubVersion": "1.11.0".

[dhasenan]

Related: #1021