LES Part 1 (#3322)

* stub implementations of light client trait

* Light provider trait

* light client sync stubs

* LES boilerplate

* stub implementation of provider for client

* skeleton and request traits

* request definitions

* new_list -> begin_list

* handle unknown packet

* revise light implementation strategy

* make verification module public

* Move all light client work to own crate

* experiment with answering requests

* buffer flow scaffolding

* remove LESv2 requests

* buffer flow basics, implement cost table

* begin status module

* implement handshake parsing and creation

* implement announcement serialization

* errors, punishment, and handshake

* handle announcements

* making announcements, clean up warnings

* allow dead code temporarily

sync/src/sync_io.rs

@@ -22,7 +22,7 @@ use ethcore::header::BlockNumber;
 use ethcore::snapshot::SnapshotService;
 use parking_lot::RwLock;
 
-/// IO interface for the syning handler.
+/// IO interface for the syncing handler.
 /// Provides peer connection management and an interface to the blockchain client.
 // TODO: ratings
 pub trait SyncIo {
@@ -70,7 +70,7 @@ pub struct NetSyncIo<'s, 'h> where 'h: 's {
 
 impl<'s, 'h> NetSyncIo<'s, 'h> {
 	/// Creates a new instance from the `NetworkContext` and the blockchain client reference.
-	pub fn new(network: &'s NetworkContext<'h>, 
+	pub fn new(network: &'s NetworkContext<'h>,
 		chain: &'s BlockChainClient,
 		snapshot_service: &'s SnapshotService,
 		chain_overlay: &'s RwLock<HashMap<BlockNumber, Bytes>>) -> NetSyncIo<'s, 'h> {