[Feature] Recirculation - move pebbles in dumpfile

[ZoeRichter]

To recirculate pebbles there need to be functions that takes the dump file containing pebble centroids, removes pebbles from the bottom of the core, and replaces them back on top of the pebbles at the top of the core, maintaining pebble IDs

Describe the feature you'd like.

Add functions to ghastly (likely either in ghastly.py or a new file) that perform this action of reading, modifying, and re-writing dump files.

Additional context.

I'm breaking the recirculation functionality into smaller chunks with issues, so the related PRs are smaller. This alone won't allow pebbles to be circulated through the core over time

How can this issue be closed?

Issue can be closed with PR that adds this functionality.