Introduce safe types for handling imbalances (#2048)

* Be a little safer with total issuance.

* PairT instead of _Pair

* Remove rev causing upset

* Remove fees stuff.

* Fix build (including tests)

* Update runtime, bump version

* Fix

* Handle gas refunds properly.

* Rename identifier

ala #2025

* Address grumbles

* New not-quite-linear-typing API

* Slimmer API

* More linear-type test fixes

* Fix tests

* Tidy

* Fix some grumbles

* Keep unchecked functions private

* Remove another less-than-safe currency function and ensure that
contracts module can never create cash.

* Address a few grumbles and fix tests

substrate/node-template/runtime/src/lib.rs

@@ -169,11 +169,10 @@ impl balances::Trait for Runtime {
 	type OnNewAccount = Indices;
 	/// The uniquitous event type.
 	type Event = Event;
-}
 
-impl fees::Trait for Runtime {
-	type TransferAsset = Balances;
-	type Event = Event;
+	type TransactionPayment = ();
+	type DustRemoval = ();
+	type TransferPayment = ();
 }
 
 impl sudo::Trait for Runtime {
@@ -200,7 +199,6 @@ construct_runtime!(
 		Indices: indices,
 		Balances: balances,
 		Sudo: sudo,
-		Fees: fees::{Module, Storage, Config<T>, Event<T>},
 		// Used for the module template in `./template.rs`
 		TemplateModule: template::{Module, Call, Storage, Event<T>},
 	}
@@ -221,7 +219,7 @@ pub type UncheckedExtrinsic = generic::UncheckedMortalCompactExtrinsic<Address,
 /// Extrinsic type that has already been checked.
 pub type CheckedExtrinsic = generic::CheckedExtrinsic<AccountId, Nonce, Call>;
 /// Executive: handles dispatch to the various modules.
-pub type Executive = executive::Executive<Runtime, Block, Context, Fees, AllModules>;
+pub type Executive = executive::Executive<Runtime, Block, Context, Balances, AllModules>;
 
 // Implement our runtime API endpoints. This is just a bunch of proxying.
 impl_runtime_apis! {