introduce cluster store

TODO

- [x] Rename Peer to Machine
- [x] Parse the new space separated bootstrap-config format
- [x] Ensure that the NodeName.ID()'s don't have collisions
- [ ] Generate initial cluster ID from a similar hash of the bootstrap-config
- [ ] Write documentation on static bootstrap

Maybe I should have said: why are we using a non-negative int for ID instead of a uint? I seem to recall a discussion in passing a little while ago about changing this but now can't find any trace :/