Proposal: Have long ghc output piped to pager.

When ghc detects errors in code, there may be long output to the console that's often more sensible to read from the top, so, when repeatedly failing to correct my code, I have every run to scroll up frantically until I find the beginning of the output. Sometimes I may even miss it and scroll to the beginning of the *previous* output, which is not good. I salvage the problem by piping the output to `less`. However, it is not so customary to pipe output from commands such as `stack test --file-watch`.

`git` invokes a pager by default for commands like `git diff`, if the output is a terminal and there are more lines to be put out than would fit. I've never heard any complaints about this behaviour; everyone seems to like it. Can we add the same feature to `stack`? I think it would be beautiful to have incremental logging (such as when building numerous dependencies) written to console, while putting long output of `ghc`, and perhaps `test` as well, to a pager.