Log the filenames agency users upload to the transition-logs server

- Bump the version of attachmentgenie/ssh to be able to do this,
  under the instruction of @dcarley.
- Add the extra arguments to the `sftp subsystem` line to
  hieradata/common.yml. Thanks to @ajlanghorn and @mattbostock for
  getting me out of a rabbit hole of which file to edit.
- Change the default destination for these new logs from syslog to
  sftp-server.log to avoid cluttering syslog.
Add a missing newline to `hieradata/common.yaml`
Include the verbose SFTP settings in a file specific to transition-logs
Merge pull request #136 from alphagov/add_transition_logs_sshd_config

Log the filenames agency users upload to the transition-logs server