Custom inspection function on Objects via .inspect() is deprecated

This is a new deprecation warning shown on Node 10 (https://github.com/nodejs/node/issues/15549).

`(node:10005) [DEP0079] DeprecationWarning: Custom inspection function on Objects via .inspect() is deprecated`

It's shown whenever an object with inspect() defined is console.logged, like `await wallet.receiveAddress()`. As these inspect()s are spread out throughout the code the change needed is not trivial. The new API for this seems a bit cumbersome: https://nodejs.org/api/util.html#util_custom_inspection_functions_on_objects.

Start by locating the inspect() definitions mentioned in the issue and review Node.js's custom inspection functions API. Update the affected objects to avoid the DEP0079 warning, then verify that console.log, including await wallet.receiveAddress(), no longer emits the deprecation warning.

Written by the indexing model from the issue text.