Fast startup on new peer joining

[pgmemk]

In current implementation the wait time for new peer to catch up could be daunting.
Use hypercore sparse magic to address that - check https://github.com/mafintosh/hypercore-multi-key to clone another peer's hyperbee and repossess with multi-key

[pgmemk]

It's fair also for the case when the device was dormant for a long time and then comes online and needs to download a copious amount of data.