Script to reduce the size of the UTXO.csv

[pkahly]

Add an experimental script that will read the utxo.csv and write a reduced version to a new file.

Parameters could include:

• block height
• amount
• fields to keep

This will allow easier experimentation with the watchlist functionality as the new file will be faster to iterate over.

[pkahly]

Script exists but needs tested on mainnet's utxo set.

Also need to add flags/arguments and possibly integrate with main.py