Removing dynamic plugins

I've noticed that the bundled plugins are severely bit-rotted. The code for dynamically loading plugins is very brittle and does not play well with the sandboxed method Haskell libraries are installed these days.

@jgm would you be opposed to a PR that ripped out dynamic plugin capabilities and replaced it with something more akin to a contrib library or just bundled the existing plugins in a way that they are compiled with the rest of the package?