DEMO: account management

[pcppcp]

Basic utilities to demo that ethereum connectivity works. This applies to the wallet shell submodule.

• [x] set private key (pk)
• [x] update the account nonce & balance from the eth node (sync)
• [ ] display account details (info)
• [x] generate a plain transaction that transfers X ether to a destination address (transfer)
• [ ] maintain list of a last N transaction hashes and display count of confirmations on request (txs)
• [x] query current block info from the node (block)

[pcppcp]

putting this into v3.1, what we need for v3.0 is already in