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

imho split out `GenID`
```
name := pcnf[0]
m = &Member{
    Name: name,
    PeerURLs: []string{url},
    ID: GenID(name),
}
```