Fix sub2eth synchronization (#172)

* ease serde version requirements (to build OE with builtin)

* trace + fix completion notifications

* check incompletion on submit

* fix compilation

* do not ask for synced blocks when queue is empty

* cargo fmt --all

* Update relays/ethereum/src/ethereum_client.rs

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

* remove closure

* fn submit_substrate_header() -> Option<RpcError>

Co-authored-by: Tomasz Drwięga <tomusdrw@users.noreply.github.com>

bridges/relays/ethereum/res/substrate-bridge-abi.json

@@ -96,6 +96,25 @@
 		"stateMutability": "view",
 		"type": "function"
 	},
+	{
+		"inputs": [
+			{
+				"internalType": "bytes",
+				"name": "rawHeader",
+				"type": "bytes"
+			}
+		],
+		"name": "isIncompleteHeader",
+		"outputs": [
+			{
+				"internalType": "bool",
+				"name": "",
+				"type": "bool"
+			}
+		],
+		"stateMutability": "view",
+		"type": "function"
+	},
 	{
 		"inputs": [
 			{

bridges/relays/ethereum/res/substrate-bridge-metadata.txt

@@ -1,5 +1,5 @@
-Last Change Date: 2020-05-01
+Last Change Date: 2020-07-03
 Solc version: 0.6.6+commit.6c089d02
-Source hash (keccak256): 0x36403636ad41082ca6c937c60ab06446cd9ef7036c178fa2f04d7c8286544d39
-Source gist: https://github.com/svyatonik/substrate-bridge-sol/blob/8b54f5f648f8685fecd52b7af1deb277922b0fc3/substrate-bridge.sol
+Source hash (keccak256): 0x3e6339beefe6786f4f26b408d4f727e03c6fd9630d692af9a7f6b46143fa308f
+Source gist: https://github.com/svyatonik/substrate-bridge-sol/blob/1d0fa475a2ba3a70a47ed2dd870568c42ec16c8c/substrate-bridge.sol
 Compiler flags used (command to produce the file): `docker run -i ethereum/solc:0.6.6 --optimize --bin - < substrate-bridge.sol`