Partial Application: Stage 1

Champion: @rbuckton
Repo: https://github.com/rbuckton/proposal-partial-application
Slides: https://docs.google.com/presentation/d/1GSnqtT1jHbilIAwCuaK2yjKNj0y6cLfJNisZDig3Nm8/edit?usp=sharing
First presented at the Sept 2017 meeting

## Example

```js
const addOne = add(1, ?); // apply from the left
addOne(2); // 3

const addTen = add(?, 10); // apply from the right
addTen(2); // 12

// with pipeline
let newScore = player.score
|> add(7, ?)
|> clamp(0, 100, ?); // shallow stack, the pipe to `clamp` is the same frame as the pipe to `add`.

const maxGreaterThanZero = Math.max(0, ...);
maxGreaterThanZero(1, 2); // 2
maxGreaterThanZero(-1, -2); // 0
```

## Syntax

```js
f(x, ?) // partial application from left
f(x, ...) // partial application from left with rest
f(?, x) // partial application from right
f(..., x) // partial application from right with rest
f(?, x, ?) // partial application for any arg
f(..., x, ...) // partial application for any arg with rest
```

The issue links the proposal repository and presentation slides but names no files, tests, or implementation entry point. Start by reading those linked materials; a completion criterion and implementation scope are not specified in the issue.

Written by the indexing model from the issue text.