decouple balances from some modules (#1641)

* decouple balances from some module by creating a new traits in support/traits
* improve decl_event

substrate/srml/contract/src/account_db.rs

@@ -21,7 +21,7 @@ use {balances, system};
 use rstd::cell::RefCell;
 use rstd::collections::btree_map::{BTreeMap, Entry};
 use rstd::prelude::*;
-use runtime_support::{StorageMap, StorageDoubleMap};
+use runtime_support::{StorageMap, StorageDoubleMap, traits::UpdateBalanceOutcome};
 
 pub struct ChangeEntry<T: Trait> {
 	balance: Option<T::Balance>,
@@ -65,7 +65,7 @@ impl<T: Trait> AccountDb<T> for DirectAccountDb {
 	fn commit(&mut self, s: ChangeSet<T>) {
 		for (address, changed) in s.into_iter() {
 			if let Some(balance) = changed.balance {
-				if let balances::UpdateBalanceOutcome::AccountKilled =
+				if let UpdateBalanceOutcome::AccountKilled =
 					balances::Module::<T>::set_free_balance_creating(&address, balance)
 				{
 					// Account killed. This will ultimately lead to calling `OnFreeBalanceZero` callback

substrate/srml/contract/src/exec.rs

@@ -18,10 +18,10 @@ use super::{CodeHash, Config, ContractAddressFor, Event, RawEvent, Trait};
 use crate::account_db::{AccountDb, DirectAccountDb, OverlayAccountDb};
 use crate::gas::{GasMeter, Token, approx_gas_for_balance};
 
-use balances::{self, EnsureAccountLiquid};
 use rstd::prelude::*;
 use runtime_primitives::traits::{CheckedAdd, CheckedSub, Zero};
 use timestamp;
+use runtime_support::traits::EnsureAccountLiquid;
 
 pub type BalanceOf<T> = <T as balances::Trait>::Balance;
 pub type AccountIdOf<T> = <T as system::Trait>::AccountId;

substrate/srml/contract/src/lib.rs

@@ -79,6 +79,7 @@ use codec::Codec;
 use runtime_primitives::traits::{Hash, As, SimpleArithmetic,Bounded, StaticLookup};
 use runtime_support::dispatch::{Result, Dispatchable};
 use runtime_support::{Parameter, StorageMap, StorageValue, StorageDoubleMap};
+use runtime_support::traits::OnFreeBalanceZero;
 use system::{ensure_signed, RawOrigin};
 use runtime_io::{blake2_256, twox_128};
 use timestamp;
@@ -369,7 +370,7 @@ impl<T: Trait> StorageDoubleMap for StorageOf<T> {
 	}
 }
 
-impl<T: Trait> balances::OnFreeBalanceZero<T::AccountId> for Module<T> {
+impl<T: Trait> OnFreeBalanceZero<T::AccountId> for Module<T> {
 	fn on_free_balance_zero(who: &T::AccountId) {
 		<CodeHashOf<T>>::remove(who);
 		<StorageOf<T>>::remove_prefix(who.clone());