rlp serialization refactor (#4873)

* fixed naming of rlp modules

* RlpStream cleanup

* appending short rlp lists (0...55 bytes) is 25% faster

* RlpStream does not use bytes module, nor trait Stream

* removed unused code from rlp module

* compiling ethcore-util with new rlp serialization

* compiling parity with new rlp serialization

* fixed compiling ethcore-light with new rlp serialization

* fixed compiling ethsync with new rlp serialization

* removed redundant comment, print

* removed redundant double-space

* replace usage of WriteBytesExt with ByteOrder

ethcore/light/src/on_demand/mod.rs

@@ -30,7 +30,7 @@ use ethcore::executed::{Executed, ExecutionError};
 use futures::{Async, Poll, Future};
 use futures::sync::oneshot::{self, Sender, Receiver};
 use network::PeerId;
-use rlp::{RlpStream, Stream};
+use rlp::RlpStream;
 use util::{Bytes, DBValue, RwLock, Mutex, U256};
 use util::sha3::{SHA3_NULL_RLP, SHA3_EMPTY_LIST_RLP};