Era change can be forced on and forced off (#3374)

* Forcing can be on or off.

* Add a testcase.

substrate/node/cli/src/chain_spec.rs

@@ -141,6 +141,7 @@ fn staging_testnet_config_genesis() -> GenesisConfig {
 				(x.0.clone(), x.1.clone(), STASH, StakerStatus::Validator)
 			}).collect(),
 			invulnerables: initial_authorities.iter().map(|x| x.0.clone()).collect(),
+			.. Default::default()
 		}),
 		democracy: Some(DemocracyConfig::default()),
 		collective_Instance1: Some(CouncilConfig {
@@ -268,6 +269,7 @@ pub fn testnet_genesis(
 				(x.0.clone(), x.1.clone(), STASH, StakerStatus::Validator)
 			}).collect(),
 			invulnerables: initial_authorities.iter().map(|x| x.0.clone()).collect(),
+			.. Default::default()
 		}),
 		democracy: Some(DemocracyConfig::default()),
 		collective_Instance1: Some(CouncilConfig {

substrate/node/executor/src/lib.rs

@@ -378,6 +378,7 @@ mod tests {
 				offline_slash: Perbill::zero(),
 				offline_slash_grace: 0,
 				invulnerables: vec![alice(), bob(), charlie()],
+				.. Default::default()
 			}),
 			contracts: Some(ContractsConfig {
 				current_schedule: Default::default(),

substrate/node/runtime/src/lib.rs

@@ -80,8 +80,8 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	// and set impl_version to equal spec_version. If only runtime
 	// implementation changes and behavior does not, then leave spec_version as
 	// is and increment impl_version.
-	spec_version: 139,
-	impl_version: 139,
+	spec_version: 140,
+	impl_version: 140,
 	apis: RUNTIME_API_VERSIONS,
 };