ska-low-cbf-fpga: Add register logging and Firmware image caching

All notable changes to this product version are listed here in user readable form.

The format is based on Keep a Changelog,
and this product adheres to Semantic Versioning.

Summary

Added

• caching option for FPGA image downloader
• FPGA register transaction logging and decoder script

Changed

• None

Deprecated

• None

Removed

• None

Fixed

• None

Security

• None