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

this is expansive and we are doing it for every http post. probably we need to keep a copy of the newest version of cluster (not a cache, since the store knows about every update).
can we add a todo for it?