Refactor collection reference

Preferring the more permissive .getCollection(x)  interface over direct member access as it allows databases [beginning with _](https://docs.mongodb.com/manual/reference/method/db.getCollection/#db.getCollection).

NumberLong data type recognition

ParameterParsingTest fix

ES6 and ES7 features in tests (import, export, async & await)

Conflicts:
	variety.js

Tests rewritten to JavaScript, npm package definition, ESLint

Dockerized tests

Add support for external results database

Introduces four new options for defining an external database
for persisting Variety results.

variety-cli mentioned in readme

Enumerate type counts for multiple types; enable secondary reads