Soft-fork will remain default behaviour, but you can now disable
either the whole mechanism (you'll lose money if you mine with this
when the majority network doesn't) or just vote against it but
otherwise go with the flow.
* Firt commit.
* First non-functional but correct implementation of BasicAuthority.
Still needs:
- Sealing infrastructure.
* Punch a hole to give miner access to key store.
* Fix test built.
* Basic version of synchronous mining.
This will seal a block whenever a new transaction comes through.
To be made better we need a timer which will wait for one second after the
last block before sealing a new one - better still would be to cooperatively
interleave blocks with other sealing nodes.
* Add tests.
* Fix minor issues from repotting.
* Address grumbles.
