Add prettier to standardize codebase

[jason-fox]

Upgrades codebase to use ES6 const and let. Standardizes code format.

• Add prettier to package.json
• Run ESLint
• Fix remaining errors

npm run lint fixes most errors and reports warnings.

npm test will start with a pretest lint run - I've not fixed the tests - currently fails since all files refer to config.js - (see #50 ) if the template is used then some tests will pass since the sanity tests rely on other microservices running

[aalonsog]

👍