This syncs from SUSE:SLE-15:Update. the slightly non-incremental
changelog can't be avoided.

- suse build key extended (bsc#1176759)
gpg-pubkey-39db7c82-5847eb1f.asc -> gpg-pubkey-39db7c82-5f68629b.asc

- actually the container key is different from the build signing
key. (PM-1845 bsc#1170347)

- add a /usr/share/container-keys/ directory for GPG based Container
verification.
- Add the SUSE build key as "suse-container-key.asc". (PM-1845 bsc#1170347)

- created a new security@suse.de communication key (bsc#1166334)

- include ptf key in the key directory to avoid it being
stripped via %doc stripping. (bsc#1044232) (forwarded request 899537 from dirkmueller)