Add Typescript dependencies for unit testing in Jest

[stijnklomp]

• Add the NPM package ts-jest to allow for unit tests in Typescirpt
  https://www.npmjs.com/package/ts-jest
• Remove any existing dependencies that are no longer needed. We will only allow unit tests written in Typescript
• Jest might require common JS instead of ES6+ in which case we will need to use Babel to convert the code
  https://stackoverflow.com/questions/35756479/does-jest-support-es6-import-export
• Add a script for the coverage report from Jest