decouple balances from some modules (#1641)

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

substrate/srml/executive/src/lib.rs

@@ -304,6 +304,7 @@ mod tests {
 	use primitives::BuildStorage;
 	use primitives::traits::{Header as HeaderT, BlakeTwo256, IdentityLookup};
 	use primitives::testing::{Digest, DigestItem, Header, Block};
+	use runtime_support::traits::Currency;
 	use system;
 
 	impl_outer_origin! {