srml-contract: Extract schedule (#1044)

* Rename Config → Schedule.

* Fetch and pass config.

* Integrate config everywhere.

* <<<E as Ext>::T as Trait> → <<E::T as Trait>

* Update roots

* Cache existential_deposit

* Update COMPLEXITY.md

* Update roots.

substrate/srml/contract/src/tests.rs

@@ -142,6 +142,7 @@ impl ExtBuilder {
 				gas_price: self.gas_price,
 				max_depth: 100,
 				block_gas_limit: self.block_gas_limit,
+				current_schedule: Default::default(),
 			}.build_storage()
 			.unwrap().0,
 		);