Allow the exportation of extended public key #159
Description
When I try to export an extended public key from my ledger, I can only find what in Bitcoin terms are called an compressed public key, a public key starting with 02 or 03. I would like the extended public key, so I can derive addresses without using the Ledger.
This requires that the Ledger can derive tz2 addresses as specified in #158
Se also the Stack Exchange issue on this
https://tezos.stackexchange.com/questions/2869/can-i-export-an-ecdsa-xpub-from-my-ledger