txdb: Include in TXDetails value of individual transaction from viewpoint of accounts and overall wallet

[pinheadmz]

This PR adds two new functions and their return values to the Details object defined in txdb.js and returned by wallet.getHistory() API calls, as well as by wallet events confirmed, unconfirmed, tx, and conflict.

The new values are walletValue which returns the total change to total wallet balance affected by this transaction, and accountValues which is an object whose keys are account IDs and values are the total balance affected to which accounts by this transaction.

The effect is that tx events and history queries can now inform the user exactly "what happened" in a transaction.

Example output is below. Notice this is a transaction that sent Bitcoin from account 0 to account 1 (as well as a few other outputs, it was randomly generated)

  {
    "hash": "c03ba942470dc0ee91ec53d2d6af9b7b67355fa8afb4f9d91ec337c71f8d6341",
    "height": 436,
    "block": "10cb8cc432c821f0b29c1431a3bb7f877dbfa6e258c614b77b86ab9b582bf787",
    "time": 1549134071,
    "mtime": 1549134002,
    "date": "2019-02-02T19:01:11Z",
    "mdate": "2019-02-02T19:00:02Z",
    "size": 324,
    "virtualSize": 324,
    "fee": 3260,
    "rate": 10061,
    "walletValue": -94054,
    "accountValues": {
      "0": -126079,
      "1": 32025
    },
    "confirmations": 8,
    "inputs": [
      {
        "value": 12458239242,
        "address": "RP9XvkG6aGrRNZVojGv8QW51RQ5uN3yUxm",
        "path": {
          "name": "default",
          "account": 0,
          "change": true,
          "derivation": "m/0'/1/0"
        }
      }
    ],
    "outputs": [
      {
        "value": 31657,
        "address": "RMUuKM8eP4xy4XqfrL8WQPqrDbhxjkqyfB",
        "path": null
      },
      {
        "value": 32025,
        "address": "rb1qydqrkmj02stgeg57kkh4hjwegmja3h38uls2se",
        "path": {
          "name": "hot",
          "account": 1,
          "change": false,
          "derivation": "m/1'/0/5"
        }
      },
      {
        "value": 54978,
        "address": "RUnrdH8PLFCT23z8ukUHdmoR1sqTbrK8Kg",
        "path": {
          "name": "default",
          "account": 0,
          "change": false,
          "derivation": "m/0'/0/5"
        }
      },
      {
        "value": 59137,
        "address": "RUg1P6822SshctwCBhtiENnov7frvGeuMK",
        "path": null
      },
      {
        "value": 12458058185,
        "address": "R9xUg3LgPHuy4f8ex4t613LzqMUP7Lp1HN",
        "path": {
          "name": "default",
          "account": 0,
          "change": true,
          "derivation": "m/0'/1/4"
        }
      }
    ],
    "tx": "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"
  }

---

TODO:

• Write tests

[codecov-io]

Codecov Report

Merging #687 into master will increase coverage by 0.04%.
The diff coverage is 96.29%.

@@            Coverage Diff             @@
##           master     #687      +/-   ##
==========================================
+ Coverage   53.38%   53.42%   +0.04%     
==========================================
  Files         104      104              
  Lines       27716    27743      +27     
  Branches     4748     4754       +6     
==========================================
+ Hits        14796    14822      +26     
- Misses      12920    12921       +1

Impacted Files	Coverage Δ
lib/wallet/txdb.js	80.3% <96.29%> (+0.42%)	⬆️

---

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