Remove the DataSources for secret, and generate the content of secrets
with the output of commands. This allows more dynamic encrypted/secure
secrets that are not just saved plain in the repository.
- Generic type is now named DataSources to remove ambiguity,
- NamePrefix is now just Name, since that's what it is,
- Secret have been split in GenericSecret and TLSSecret,
The code, test and examples have been updated to work with these new
types.