suggestion: improve warning on xpub / private key dialogs for deterministic wallets

[markblundeberg]

According to BIP32:

knowledge of a parent extended public key plus any non-hardened private key descending from it is equivalent to knowing the parent extended private key (and thus every private and public key descending from it).

In other words, if a user shares their xpub along with just one private key, then the entire wallet is compromised just as if the user had revealed the seed mnemonic. Currently neither the Wallet|Information dialog nor the per-address private key dialog (Right click -> private key) give any scare warnings about this. I suggest that one or both should have a warning added to that effect.

(currently there is only such a warning on Wallet|Private Keys|Export)

[cculianu]

This is a very good suggestion. Will keep open.