Haskell quick dev mode

[charleso]

Currently the dev loop for haskell projects is to restart the webapp every time a template changes (which is best done in ghci but is still manual).

We can do better.

The current thinking is that we use hint to reload the haskell dynamically. Some proof-of-concept work has been started here, with some success.

https://github.com/ambiata/loom/compare/wip/hint

The things that will need to be done for this to be production ready:

• Calculate GHC_PACKAGE_PATH for a haskell project, could live in mafia
• Mafia "setup" which initialises a haskell project, but doesn't compile anything. Otherwise we would want to run build and ignore any errors.
• Either merge Add reload haskell-hint/hint#26 or fork to ambiata
• Run a separate http server to intercept calls to the real application, show any build errors or wait until it is restarted on changes