Some config keys changed as well since the last update

This reverts commit 2535de6a.

While it's not stricly required by everyone it doesn't require any
extra implementation right now and is required by all frontend apps
in the future, so including it should make the initial setup easier.

It gets called during composer install which we need when deploying
without dev packages.

Disabling scripts would work, but then the symfony install commands
would be skipped too...

This mainly means the keycloak config moves to a separate bundle

The core bundle is now available on packagist

While the starter bundle gives a nice example for how to integrate an API
it makes setting up a new server harder because the user usually already
has a bundle in mind that he/she wants to add.

So remove it and instead make it easier to add bundles by improving the docs

This is now handled by the composer.json in .gitlab-ci if needed

symfony now requires framework.secret to be set
the person entity is gone from the core bundle, so no need to implement it.