Stash/controller model for staking (#1782)

* First steps to stash/controller separation

* More drafting

* More drafting

* Finish draft.

* Optimisation

* Remove accidental commit

* Make it build.

* Fix linked map for traits.

* Fix Option<_> variant.

*  Improve naming a tad

* Rebuild runtime

* Builds!

* First test.

* Bump RT version

* Minor fix

* Update Mock

* adds the correct reward testcase (+staking eras which was already ok)

* fixes the basic staking testcase to work properly (along with a small fix in the module)

* New logic to avoid controller transferring stash.

* Fix some build issues.

* adding some comments to tests

* Fix impls.

* adds a few more lines to explain the test case

* More fixes.

* gets the basic test up and running again

* Fix rest of build

* Rebuild wasm

* Fix docs.

* fix staking test with new chnages

* updating some tests, pending questions

* More working tests

* adds double staking test

* Docs

* remove invalid slashing test

* Payee stuff.

* Fix build

* Docs

* Fix test

* Fix a couple of tests

* Layout plan for finishing tests before Pragmen

* Add some working tests

* re-build staking and reward tests

* Add more tests

* fix offline grace test

* Nominator should have payee checked for cleanup

* adds more nomination tets

* adds validator prefs tests

* Fix and clean up some TODOs

* Fix a couple of issues

* Fix tests

* noting warnings from tests

* final fix of local tests

* Fix slot_stake bug

* Half baked test

* Add logic to limit `unstake_threshold` set in storage

* Make sure to check before writing!

Almost forgot this one

* Move a couple of comments

* fix last broken slot_stake test

* Ignore broken test

substrate/srml/fees/src/lib.rs

@@ -19,10 +19,12 @@
 // Ensure we're `no_std` when compiling for Wasm.
 #![cfg_attr(not(feature = "std"), no_std)]
 
-use srml_support::{dispatch::Result, traits::ArithmeticType, StorageMap, decl_event, decl_storage, decl_module};
+use srml_support::{
+	dispatch::Result, StorageMap, decl_event, decl_storage, decl_module,
+	traits::{ArithmeticType, ChargeBytesFee, ChargeFee, TransferAsset, WithdrawReason}
+};
 use runtime_primitives::traits::{
-	As, ChargeBytesFee, ChargeFee,
-	TransferAsset, CheckedAdd, CheckedSub, CheckedMul, Zero
+	As, CheckedAdd, CheckedSub, CheckedMul, Zero
 };
 use system;
 
@@ -96,7 +98,7 @@ impl<T: Trait> ChargeFee<T::AccountId> for Module<T> {
 		let current_fee = Self::current_transaction_fee(extrinsic_index);
 		let new_fee = current_fee.checked_add(&amount).ok_or_else(|| "fee got overflow after charge")?;
 
-		T::TransferAsset::remove_from(transactor, amount)?;
+		T::TransferAsset::withdraw(transactor, amount, WithdrawReason::TransactionPayment)?;
 
 		<CurrentTransactionFee<T>>::insert(extrinsic_index, new_fee);
 		Ok(())
@@ -107,7 +109,7 @@ impl<T: Trait> ChargeFee<T::AccountId> for Module<T> {
 		let current_fee = Self::current_transaction_fee(extrinsic_index);
 		let new_fee = current_fee.checked_sub(&amount).ok_or_else(|| "fee got underflow after refund")?;
 
-		T::TransferAsset::add_to(transactor, amount)?;
+		T::TransferAsset::deposit(transactor, amount)?;
 
 		<CurrentTransactionFee<T>>::insert(extrinsic_index, new_fee);
 		Ok(())

substrate/srml/fees/src/mock.rs

@@ -20,12 +20,15 @@
 
 use runtime_primitives::BuildStorage;
 use runtime_primitives::{
-	traits::{IdentityLookup, BlakeTwo256, TransferAsset},
+	traits::{IdentityLookup, BlakeTwo256},
 	testing::{Digest, DigestItem, Header},
 };
 use primitives::{H256, Blake2Hasher};
 use runtime_io;
-use srml_support::{impl_outer_origin, impl_outer_event, traits::ArithmeticType};
+use srml_support::{
+	impl_outer_origin, impl_outer_event,
+	traits::{ArithmeticType, TransferAsset, WithdrawReason}
+};
 use crate::{GenesisConfig, Module, Trait, system};
 
 impl_outer_origin!{
@@ -48,8 +51,8 @@ impl<AccountId> TransferAsset<AccountId> for TransferAssetMock {
 	type Amount = u64;
 
 	fn transfer(_: &AccountId, _: &AccountId, _: Self::Amount) -> Result<(), &'static str> { Ok(()) }
-	fn remove_from(_: &AccountId, _: Self::Amount) -> Result<(), &'static str> { Ok(()) }
-	fn add_to(_: &AccountId, _: Self::Amount) -> Result<(), &'static str> { Ok(()) }
+	fn withdraw(_: &AccountId, _: Self::Amount, _: WithdrawReason) -> Result<(), &'static str> { Ok(()) }
+	fn deposit(_: &AccountId, _: Self::Amount) -> Result<(), &'static str> { Ok(()) }
 }
 
 impl ArithmeticType for TransferAssetMock {