Support Sub Accounts in a Developer Wallet

[gregsantos]

A Flow developer wallet should support viewing and/or include a management interface for sub accounts

We need a demo of how sub accounts (and their assets?) can be viewed and/or managed.
Management may include editing or destroying the account "Rage Quit" via the Sub Account Manager Resource or removing keys or withdrawing assets to the main account.
This can be added to the dev-wallet, extension wallet, or both.

May utilize an FCL Wallet utility to expose all child accounts to wallet providers such that they can show all sub-accounts of the current parent and their corresponding assets by querying the resource on the parent to get this probably.

[justinbarry]

Re: onflow/cadence#2151