Add comprehensive matrix of GHC bindists

### General summary/comments

I attempted to do a `stack setup` on MacOS of the integersimple variant of GHC 8.0.2. However, that's apparently not currently supported. It's my understanding that interested users are currently expected to provide these bindist variations, but I didn't have much luck finding a list that shows what's currently available.

Ideally, I think it'd be great to have a table somewhere easily discoverable (perhaps even accessible via the CLI itself) with a format sort of like:

| GHC Version | Host architecture | Host platform | Target architecture | Target platform | GHC variant (standard / integersimple) |
| -------------|-------------------|---------------|--------------------|-----------------|----