Path issue with serialized wallets migrated from pre-0.15 to 0.15

[schildbach]

When protobuf-deserializing a pre-0.15 wallet with bitcoinj 0.15, for each keychain an account path of m/0' is assumed. If the account path was customized before, it will be wrong after deserialization.

We should probably find a way to customize the default applied in https://github.com/bitcoinj/bitcoinj/blob/master/core/src/main/java/org/bitcoinj/wallet/DeterministicKeyChain.java#L811, such that wallets that know they've been using a different account path before can use that for easier migration.

This issue was found by @oscarguindzberg

[oscarguindzberg]

Original email thread https://groups.google.com/forum/#!topic/bitcoinj/nTzQdwrs2n4