legacy-importer: show progress while importing
Added mail script

You now can get all mail addresses for pools via cmdline with
mail_addresses_for_pools POOL_NAME:

Example:
  $ python manage.py mail_addresses_for_pools Legacy | wc -l
  3901

Additionally you can mail an email to all people of a pool via
"mail POOL_NAME SUBJECT PATH_TO_EMAIL_TEMPLATE [-d delay]". With delay you can
specify the amount of time to wait between mails (default: 0.5).

Example:
  $ python manage.py mail Legacy "Hello World" /tmp/template -d 5