refresh BwAuthority run_scan.sh and deployment instructions
The deployment instructions for BwAuthority (https://gitweb.torproject.org/torflow.git/blob_plain/HEAD:/NetworkScanners/BwAuthority/README.BwAuthorities) can be cleaned up. For example, fairly recent versions of python-sqlalchemy (0.7.8-1) and python-elixir (0.7.1-1) are packaged in debian squeeze.
Also https://gitweb.torproject.org/torflow.git/blob_plain/HEAD:/NetworkScanners/BwAuthority/run_scan.sh could be cleaned up.