build: make sure we fully comply with the Angular Package Format (APF)

[dsebastien]

cfr Angular package format (APF): https://docs.google.com/document/d/1CZC2rcpxffTDfRDs6p1cfbmKNLA6x5O-NtkJglDaBVs/preview

Things to do we've identified so far:

• add missing properties in package.json for each package
• add missing properties in tsconfig.json for each package
• sub-packages: add missing sub-packages support in the build.sh script
• sub-packages: add sub-package for e2e support in stark-core as example and make sure it works. Concrete example: https://github.com/angular/angular/tree/master/packages/core/testing and https://github.com/dherges/ng-packagr#secondary-entry-points
• add testing folder to each package (and review how it's handled in angular build)

[ncedric]

Done