Support custom HD Wallet derivations via API

Description:
Currently it seems that the generation of new accounts are a simple “+1” of the last created account/wallet. Nevetheless an API allowing applications to generate new wallets using a custom derivation string beyond m/44’/60’/0’/0/0 and subsequent may improve some privacy use cases.

Purpose:
Allow multiple addresses/wallets with a custom derivation string create organized address sets.

Extension/Mobile/Both:
Both.

Images/Attacments: