Support various data retention policies

[Duncan McGreggor]

Due to the issue in #59, we're taking a more creative (and flexible) approach to deleting records.

0.7.0 Tasks:

• Add "active" and "deleted" fields to metadata
• Update rm command to not delete the record, but rather update the metadata
  • Note: this will close #59
• Add support for updating a record to "inactive" (active=false)
• Add command to list deleted records
• Update listing displays to optionally include status (active, inactive, deleted)
• Add set status (active, inactive, deleted) subcommand

0.9.0 Tasks:

• Add config section [retention]
  • add option purge_on_shutdown (default false)
  • add option archive_deletes (default true)
  • add option delete_inactive (default false)
• Add config section [output]
  • add option show_inactive
  • add option show_deleted
• Add support for executing callbacks on shutdown
• Add logic and tests for new config options above:
  • Add testing configs and the ability to use them for specific tests
  • Add logic for scanning all records and completely removing those that have been labeled as deleted
  • Add logic for scanning all inactive records and setting them to deleted
  • Update output opts to add flags for showing inactive/deleted
  • Update output results to show/hide based upon these flags
• Add/update subcommands
  • config re-init
  • Rename rm module to delete and rename the subcommand, too
  • delete inactive ... note that this implies a two-stage delete process
  • purge deleted
  • purge inactive ... this would skip the two stage process and go right to "delete"