Templating/files related to extracted lead to duplication

[palmskog]

I've come to the conclusion that the extracted approach to specify metadata for subprojects (which I introduced) is a failure, leading for example to duplication and redundancy. These subprojects could instead have their own meta.yml file or be handled completely manually.

It should be straightforward to excise everything related to extraction from the templates repo, and I will open a PR to this effect in the near future.

[Zimmi48]

At least the parts in the README do not look to me like they could be handled from their own template. Somehow, this looks directly related to the more general question of how to handle monorepos (several packages sharing a single repository and thus having a shared README).