Added 'package' property with Jinja2 support.

The added property allows for setting indidivual package names.

Usage:

    pyload:
      api: xxx
      username: xxx
      password: xxx
      parse_url: yes
      queue: no
      hoster:
        - xxx
      multiple_hoster: no
      package: 'Series - {{series_name}} - {{series_id}}'