Transaction Fee Module (#1648)

* wip

* Split bytes fee charging and charging by amount into different traits.

* Move to edition 2018.

* Implemented charge fee traits for fees module.

* Implemented 'on_finalise' for fee module.

* Updated fees finalize impl.

* Renaming and documentation update.

* Added overflow & underflow check for fee calculation.

* Added mock and unit tests for fee module.

* More unit tests for fees module.

* Fixed srml-executive unit tests.

* Remove transaction base/bytes fee from balances module, fix unit tests.

* fix compile error

* Fixed unit test.

* Minor fixes.

* Bump spec version.

* Bump spec version.

* Updated fees module and runtime wasm.

* Fees module code style improvement; updated runtime wasm.

* Bump spec and impl version.

substrate/srml/contract/src/tests.rs

@@ -27,6 +27,7 @@ use runtime_io;
 use srml_support::{StorageMap, StorageDoubleMap, assert_ok, impl_outer_event, impl_outer_dispatch, impl_outer_origin};
 use substrate_primitives::{Blake2Hasher};
 use system::{self, Phase, EventRecord};
+use fees;
 use {wabt, balances, consensus};
 use hex_literal::*;
 use assert_matches::assert_matches;
@@ -44,7 +45,7 @@ mod contract {
 }
 impl_outer_event! {
 	pub enum MetaEvent for Test {
-		balances<T>, contract<T>,
+		balances<T>, contract<T>, fees<T>,
 	}
 }
 impl_outer_origin! {
@@ -88,6 +89,11 @@ impl consensus::Trait for Test {
 	type SessionKey = UintAuthorityId;
 	type InherentOfflineReport = ();
 }
+impl fees::Trait for Test {
+	type Event = MetaEvent;
+	type Amount = u64;
+	type TransferAsset = Balances;
+}
 impl Trait for Test {
 	type Call = Call;
 	type Gas = u64;
@@ -165,8 +171,6 @@ impl ExtBuilder {
 		t.extend(
 			balances::GenesisConfig::<Test> {
 				balances: vec![],
-				transaction_base_fee: 0,
-				transaction_byte_fee: 0,
 				existential_deposit: self.existential_deposit,
 				transfer_fee: self.transfer_fee,
 				creation_fee: self.creation_fee,