* Price oracle support. For approved keys only, an oracle report can
be submitted to help set the HNT price, which in turn determines how
many DC an HNT creates.
* Improved password hashing. The existing pbkdf2 password stretching
is not current best practice for password stretching and has slow
or outdated implementations. Switch the default password hash to the
one recommended in libsodium (argon2id13) with sensitive settings.
* Expose an `upgrade` command to upgrade an existing wallet to the
latest version (which is the new argon2id13 hasher)of the given
type. This upgrade command can also be used to upgrade a basic wallet
to a sharded one or vice-versa.
