build: lighten bundles

[dsebastien]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[x] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#got-a-question-or-problem

Current behavior

When running npm run build:prod, we get the following warnings:

WARNING in asset size limit: The following asset(s) exceed the recommended size limit (244 KiB).
This can impact web performance.
Assets:
  vendor.b569b7e920e5585e7943.chunk.js (1.33 MiB)

WARNING in entrypoint size limit: The following entrypoint(s) combined asset size exceeds the recommended limit (244 KiB). This can impact web performance.
Entrypoints:
  polyfills (1.33 MiB)
      runtime~polyfills.9e149de364f4530dd6d8.bundle.js
      vendor.b569b7e920e5585e7943.chunk.js
      polyfills.9492ba1253ac1fb01456.chunk.js
  main (1.35 MiB)
      runtime~main.74f27cbd50be5b80d944.bundle.js
      vendor.b569b7e920e5585e7943.chunk.js
      main.3fde0b4403b0e4fc0cd8.css
      main.d007e62b259e907e5c67.chunk.js


WARNING in webpack performance recommendations:
You can limit the size of your bundles by using import() or require.ensure to lazy load some parts of your application.
For more info visit https://webpack.js.org/guides/code-splitting/

We should analyze these bundles and understand what's taking that much space / how to limit. If we still have that after clean up, then we should find a way to increase the limits.

Expected behavior

No warnings for bundle size.

Minimal reproduction of the problem with instructions

What is the motivation / use case for changing the behavior?

Environment

Angular version: X.Y.Z
Stark version: X.Y.Z


Browser:
- [ ] Chrome (desktop) version XX
- [ ] Chrome (Android) version XX
- [ ] Chrome (iOS) version XX
- [ ] Firefox version XX
- [ ] Safari (desktop) version XX
- [ ] Safari (iOS) version XX
- [ ] IE version XX
- [ ] Edge version XX
 
For Tooling issues:
- Node version: XX  
- Platform:  

Others:

[christophercr]

~~Bocked by #883~~