Remove As (#2602)

* Start to remove the `As` bound on `SimpleArtithmetic`

This just introduces standard numeric bounds, assuming a minimum of
`u32`. Also included is a saturating from/into trait allowing ergonomic
infallible conversion when you don't care if it saturates.

* Remove As from Balances trait

* Remove As from Aura module

* Remove As from Babe module

* Expunge `As` from contract

* Council module

* Democracy

* Finality tracker

* Grandpa

* First bit of indices

* indices

* Line lengths

* session

* system

* Staking

* Square up all other uses of As.

* RHD update

* Fix build/test

* Remove As trait

* line widths

* Remove final As ref

* Update srml/staking/src/lib.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Update core/client/src/cht.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Update core/client/db/src/light.rs

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* Apply suggestions from code review

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>

* whitespace

* Apply suggestions from code review

Co-Authored-By: Bastian Köcher <bkchr@users.noreply.github.com>
Co-Authored-By: André Silva <andre.beat@gmail.com>

* Bring back u32 check for number on CLI

substrate/core/finality-grandpa/src/environment.rs

@@ -34,7 +34,7 @@ use grandpa::{
 };
 use runtime_primitives::generic::BlockId;
 use runtime_primitives::traits::{
-	As, Block as BlockT, Header as HeaderT, NumberFor, One, Zero, BlockNumberToHash,
+	Block as BlockT, Header as HeaderT, NumberFor, One, Zero, BlockNumberToHash,
 };
 use substrate_primitives::{Blake2Hasher, ed25519, H256, Pair};
 use substrate_telemetry::{telemetry, CONSENSUS_INFO};
@@ -669,7 +669,7 @@ where
 			&*self.inner,
 			&self.authority_set,
 			&self.consensus_changes,
-			Some(As::sa(self.config.justification_period)),
+			Some(self.config.justification_period.into()),
 			hash,
 			number,
 			(round, commit).into(),

substrate/core/finality-grandpa/src/lib.rs

@@ -157,7 +157,7 @@ pub struct Config {
 	/// Justification generation period (in blocks). GRANDPA will try to generate justifications
 	/// at least every justification_period blocks. There are some other events which might cause
 	/// justification generation.
-	pub justification_period: u64,
+	pub justification_period: u32,
 	/// The local signing key.
 	pub local_key: Option<Arc<ed25519::Pair>>,
 	/// Some local identifier of the voter.