Create PR for BIP44 support work for Bitcoinj

[gary-rowe]

The BIP44 support work is currently held in our Bitcoinj-Alice fork. It would be better if this work could be generalised and pushed upstream for other projects to benefit from.

This is a complex change and may require a lot of support work before a PR would be accepted upstream. For this reason it has to occur after the first release of the project.

[devrandom]

I have a general implementation that allows a DKC to have an arbitrary account derivation path. Should I'll compare my implementation to yours and see which one makes more sense to create a PR out of?

(Cc @mikehearn)

[jim618]

It sounds similar.
I found the serialisiing and deserialising of the wallets to be the least general part of the bitcoinj-alice code - not really good enough for a general purpose library.

[devrandom]

Yes, I had the same experience, due to the use of static functions. Ended up with some factory classes to generalize.

[devrandom]

Created bitcoinj/bitcoinj#339