More robust punishment (#3952)

* Introduce new option "always force new era".

* Take appropriate action, even for small offences.

- Deselect the offender in all circumstances
- Ensure that deselection forces a new era
- Ensure that forcing a new era works with the always-forcing.

* Bump runtime

substrate/node/runtime/src/lib.rs

@@ -81,7 +81,7 @@ 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: 189,
+	spec_version: 190,
 	impl_version: 190,
 	apis: RUNTIME_API_VERSIONS,
 };