Write initial pretty-printer

[sshine]

Use quchen's prettyprinter for this.

This task may be broken into parts, e.g.:

• Set up dependencies, create module, perform basic imports and function stub.
  Note: Any subsequent sub-part depends on this task being in-place.
• Write a sub-part of the pretty-printer that only addresses a particular piece of syntax, e.g.:
  ., ?, .foo, .[], true / false, `"(true)"
• Write pretty-printer for binary operators that respects precedence and associativity. The best way that I am currently aware of is demonstrated in Lira's prettyprinter, but other suggestions or sources of inspiration are very welcome.

For each of these tasks, initially you can choose to not worry if the output is actually pretty.