EIPs 155, 160, 161 (#2976)

* The front-end for each hard-fork, also EIP-160.

* Address EIP161 a/c

* Include EIP-161b

* EIP-161 part d.

* Fix test build.

* Fix one test, add another.

* Fix use of bloom & renaming.

* Initial groundwork for EIP-155

* Fix minor bug.

* Fix all tests finally.

* Rest of EIP-155.

* Add tests for EIP-155 algorithm.

Update transaction tests validation.

* Minor reformat.

* Address grumbles.

* Remove unused code.

* Fix SUICIDE gas mechanism and add consensus tests.

* Remove commented code.

* Set Frontier hardfork block number

* Fix warning.

* Transaction tests,

sync/src/api.rs

@@ -42,7 +42,7 @@ pub struct SyncConfig {
 	/// Max blocks to download ahead
 	pub max_download_ahead_blocks: usize,
 	/// Network ID
-	pub network_id: U256,
+	pub network_id: usize,
 	/// Main "eth" subprotocol name.
 	pub subprotocol_name: [u8; 3],
 	/// Fork block to check
@@ -55,7 +55,7 @@ impl Default for SyncConfig {
 	fn default() -> SyncConfig {
 		SyncConfig {
 			max_download_ahead_blocks: 20000,
-			network_id: U256::from(1),
+			network_id: 1,
 			subprotocol_name: *b"eth",
 			fork_block: None,
 			warp_sync: false,