Changes the way Renovate treats renovate config inside `package.json` files. Before, config used to be applied only to that particular file, meaning that it was not applied for the rest of a monorepo, or for other package managers like Docker. Now, any `renovate` section inside the repository’s root `package.json` will be applied globally, just the sams as if it were contained within a `renovate.json` file. This means there is no longer any case where you *must* have a `renovate.json` file instead of `package.json`.

Closes #1323

BREAKING CHANGE: renovate config in `./package.json` is now applied to whole repository, and renovate config inside non-root `package.json` files is now ignored.