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

[gtklocker]

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.