changes PasswordStore.encrypt behavior when .gpg-id support is off
(default):
old:
* ignores passed in keyID
* encrypt with first public key in keychain (gopenPGP), or entire
keychain (ObjectivePGP)
new:
* honor passed in keyID
* encrypt with all keys in keychain
this is refactoring support, so that we can notice changes in how the
underlying APIs are called, and make changes intentionally when needed,
instead of accidentally.