Adds cpak export support to cgeo.

This augments all geometry types (in a TypeScript-friendly way) with a toCpak method returning a string.

Additionally, the static method Geometry.fromCpak takes a string and returns the appropriate geometry object.

import * as cgeo from 'cgeo';
import 'cgeo-wkt';
import 'cgeo-cpak';

const geom = Geometry.fromCpak('');

console.log(geom.toWKT());

The MIT License

Copyright (c) 2017 BusFaster Ltd