N-dimensional bounding-boxes

This might be a tad too low-brow for your tastes, but is there any chance we could export a simple polymorphic n-dimensional `BoundingBox` (or similarly named) type from this library?

Given the universality of this package (and how it ties in quite nicely with the `V[N]` types)

Since there is no 'standard' type, people keep defining their own, making interop a bit of a trudge (and Haskellers don't trudge; they stride, right).

My own definition looks a bit like this:

```haskell
data BoundingBox v = BoundingBox { cornerOf :: v, sizeOf :: v } deriving (Show, Eq)
```

The suffix is partly for aesthetics (`cornerOf box` reads nicely; `of` is a nice synonym for `flip (^.)`, come to think of it), partly a guide for lens generation.

This got a bit long (sorry), but I have a final question: if this functionality should *not* be part of `linear`, do you have a suggestion for where it might fit in? Is there already a nice library that *could* become the de-facto standard? Where should I turn for this type of discussion?

Thanks for the good work.