Remove the X-GPG-Encrypt-Cc header setting.

I could not find any documention on this, it seems like this was a gpg-mailgate specific option but we now read in recipients directly from the command-line arguments.
Add keymap_only configuration, to ignore public_keys list.

This means the keymap will be exclusively used to determine which email addresses to sign with which keys.
Merge branch 'master' of github.com:uakfdotb/gpg-mailgate