Updates lighthouse to the latest networking spec
- Sync re-write (#496)
- Updates to the latest eth2 networking spec (#495)
- Libp2p updates and improvements
* add logging functionality for aligning key value pairs after the main messages
* move to own crate, change default message width to 40
* use FullFormat in validator_client (CompactFormat is not compatible with aligning)
* move logging to eth2/utils/logging
* Fix syncing bugs by recursively attempting to process parents in the import queue, change BlockRootsIterator
* Swap from crossbeam channel to tokio mpsc
* Recursion fix
* Remove exess block processing
* Fix network lag, correct attestation topic
* Correct network poll logic
* Overhaul of SimpleSync and modify BlockRootsIterator to return start_slot
* Fix bug in tests relating to StateRootsIterator
* Remove old, commented-out heartbeat code.
* Tidy docs on import queue enum
* Change source logging msg in simple sync
* Rename function parameter in simple sync
* Use `BestBlockRootsIterator` in `reduced_tree`
* Update comments for `BestBlockRootsIterator`
* Fix duplicate dep in cargo.toml
This is a massive commit which restructures the workspace, adds a very
basic, untested, validator client and some very basic, non-functioning
gRPC endpoints to the beacon-node.
