Scan Diffing

[rye]

Part of #43.

As was done before, but this time coming entirely from a database.

• [ ] For each plugin, identify each plugin instance in both scans.
  • [ ] If the plugin is missing in either L or R, then it could be reported as either updated or removed.
  • [ ] If the plugin is present in both L and R, then report any differences in subsequent detections.