message: fix(core): improve GenerateAddressOptions type
  The `index` and `threshold` types are in fact optional.
  Sadly the lodash `_.isInteger()` method does not have the proper type
  annotations so we have to do a little bit of casting.
  Issue:
diff: @@ -154,9 +154,9 @@ export interface GenerateAddressOptions {
  pub: string;
  aspKeyId?: string;
  }[];
  - threshold: number;
  + threshold?: number;
  chain?: number;
  - index: number;
  + index?: number;
  segwit?: boolean;
  bech32?: boolean;
  }
  @@ -1095,7 +1095,7 @@ export abstract class AbstractUtxoCoin extends BaseCoin {
  let signatureThreshold = 2;
  if (_.isInteger(threshold)) {
  - signatureThreshold = threshold;
  + signatureThreshold = threshold as number;
  if (signatureThreshold <= 0) {
  throw new Error('threshold has to be positive');
  }
  @@ -1105,8 +1105,8 @@ export abstract class AbstractUtxoCoin extends BaseCoin {
  }
  let derivationIndex = 0;
  - if (_.isInteger(index) && index > 0) {
  - derivationIndex = index;
  + if (_.isInteger(index) && (index as number) > 0) {
  + derivationIndex = index as number;
  }
  const path = '0/0/' + derivationChain + '/' + derivationIndex;
  