Archive as a node

Issue Summary

Now that schedules are nodes it'd make sense for archives to be nodes as well. The plan looks to be:

• Update to:
  • Rename {station_archive} to {station_archive_item} and add a schedule_nid field.
  • Create a new {station_archive} table with fields for the values that are currently stored in the module's settings (promote_scheduled, delete_unscheduled, unscheduled_title, import, import_dir, remove, remove_older_than) as well as new settings (schedule_url, schedule_nid, increment).
  • Rename {station_program} to {station_archive_program} and add an archive_nid field.
  • Create a new station_archive node with the current archive settings.
• Add a station_archive node type.
• Implement hook_(load/insert/update/delete) functions for the station_archive nodes.
• Add an XML-RPC function to provide a list of programs on a given schedule.
• Add a cron job to grab the list of programs from the schedule and populate the {station_archive_program} table.

I'll tackle he last two first, as a separate issue.