When processing `publicKeys` entries, handle entries that contain
multiple public keys (i.e. gpg --show-key returns multiple `pub`
lines) properly, setting the trust level for each key.
PR #2897
(cherry picked from commit 620ed197f3)
The [throw-keyids](https://www.gnupg.org/gph/en/manual/r2110.html)
option "hides the receiver of the encrypted data as a countermeasure
against traffic analysis." However, it also slows down decryption, and
even breaks some applications; see e.g.
https://github.com/open-keychain/open-keychain/issues/626
I think the sane default would be to leave it off, just as it is off
by default in gpg. The typical user will probably not need this level
of security, and will probably prefer a better user experience (faster
decryption and compatibility with a wider range of applications).
Closes#838
