Be specific about the BitVec generic arguments (#830)

* Be specific about the `BitVec` generic arguments

Currently we use the default generic arguments for `BitVec`. This means
we use `BigEndian` and `u8`. These default values are not stable, with
`0.17` of the `BitVec` crate this changes. To make sure we don't break
anything in the future, make sure we explictly set the generics.

* Update `spec_version`

polkadot/runtime/kusama/src/lib.rs

@@ -77,7 +77,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	spec_name: create_runtime_str!("kusama"),
 	impl_name: create_runtime_str!("parity-kusama"),
 	authoring_version: 2,
-	spec_version: 1046,
+	spec_version: 1047,
 	impl_version: 0,
 	apis: RUNTIME_API_VERSIONS,
 };