Rune balances

[casey]

This is ready for review!

I'm not sure what the right output format should be. Should it be grouped by rune or grouped by output?

Grouped by output:

{
  "outpoint": {
    "rune": "balance",
    "rune": "balance",
  },
  "outpoint": {
    "rune": "balance",
    "rune": "balance",
  }
}

Grouped by rune:

{
  "rune": {
    "outpoint": "balance",
    "outpoint": "balance",
  },
  "rune": {
    "outpoint": "balance",
    "outpoint": "balance",
  }
}

Our not grouped at all:

{
  ["outpoint", "rune", "balance"],
  ["outpoint", "rune", "balance"],
  ["outpoint", "rune", "balance"]
}