add GUID to flat, filtered_flat

## Source

https://github.com/ArctosDB/arctos-roadmap/issues/31

## Summary

* add appropriate identifiers so that a copy of flat can be used to build UI, be shared, etc.
* do whatever is possible to minimize UI changes; ideally this would be completely unnoticed by users of the local AI

## User Interface Changes

minimal

## Data Structure Changes

in the cache