To avoid json-in-json-in-json the metadata is directly put in a file and
the values do not need to be quoted anymore.
The current configuration features only json-in-json.

Add a kernel version in dracut command-line options.

This script allows to by-pass shacache/shadir: execute ```40upload-image.sh```
instead of ```35install-image-directly.sh```.

- Do not enable EFI STUB mode when compiling the kernel. dracut already
  takes care of embedding an efi stub in the efi application image. See
dracut options "uefi" and "uefi_stub".
- Add examples of .config tampering (but comment them all for now).