Update and prune dependencies in Lumino 2

[afshin]

trafficstars

After we merge https://github.com/jupyterlab/lumino/pull/319, we should audit the dependencies and devDependencies of the packages (and the meta-package) and make sure they are up to date. We have a lot of warnings in the build logs and console output and we are using outdated versions of tools like ESLint, among others (e.g., we can probably change the lib options of our tsconfig files to ES6 now).

Relevant issues and PRs

• [x] #319
• [x] #330
• [ ] #332

[fcollonval]

As commented in #330, it will be nice to drop webpack and to use rollup for the tests to remove any inconsistency between the packager used for publishing and for testing.

[blink1073]

The only remaining warning is:

warning "@jupyterlab/buildutils > verdaccio > [email protected]" has unmet peer dependency "typanion@*".

I'm closing this one as complete.