Transaction timestamp condition (#4419)

* Transaction timestamp condtiion

* Updated docs

* Updated docs

* Check agains last block timestamp

ethcore/src/blockchain/update.rs

@@ -9,6 +9,8 @@ use super::extras::{BlockDetails, BlockReceipts, TransactionAddress, LogGroupPos
 pub struct ExtrasUpdate<'a> {
 	/// Block info.
 	pub info: BlockInfo,
+	/// Block timestamp.
+	pub timestamp: u64,
 	/// Current block uncompressed rlp bytes
 	pub block: &'a [u8],
 	/// Modified block hashes.