Satochip applet v0.12-0.1: support Secure Import from SeedKeeper
Satochip applet v0.12-0.1: support Secure Import from SeedKeeper

Secure Import allows to import an encrypted masterseed (16-64 random bytes) from a SeedKeeper and use it as BIP32 masterseed.
Encryption of the secret is done with a shared key obtained via ECDH with the authentikeys of the 2 devices as static keys.

* add importBIP32EncryptedSeed()
* add importTrustedPubkey() and exportTrustedPubkey()
* add card_label() to set/get a card label
* refactor: authentikey is now initialized at setup
* add export_authentikey() which is very similar to get_BIP32_authentikey()
    except that it returns authentikey even if the card is not seeded.
    This is needed because the authentikey is used to generate the shared
    encryption key when importing from a SeedKeeper.

Merge branch 'add-secure-channel'

Toporin/SatoChipApplet