Initial commit of module and working POC scripts

* siphon.db.DBManager: Uses a simple sqlite database to keep track of
  files that have been transferred
* siphon.manager.RemoteFileManager: Uses SFTP to check the configured
  hashes file on the remote server, download it when it's not being
  updated, and add anything new to the local database to be queued up
  for downloading
* siphon.util: Convenience stuff for ConfigParser and argparse
* bin/generate-sums.sh: The script that should be periodically run on
  the remote server to handle efficient hash checks on new files, so
  that the local script can subsequently grab new file info in an
  automated fashion