Fixes for misbehavior reporting in AuthorityRound (#8998)

* aura: only report after checking for repeated skipped primaries

* aura: refactor duplicate code for getting epoch validator set

* aura: verify_external: report on validator set contract instance

* aura: use correct validator set epoch number when reporting

* aura: use epoch set when verifying blocks

* aura: report skipped primaries when generating seal

* aura: handle immediate transitions

* aura: don't report skipped steps from genesis to first block

* aura: fix reporting test

* aura: refactor duplicate code to handle immediate_transitions

* aura: let reporting fail on verify_block_basic

* aura: add comment about possible failure of reporting

ethcore/src/engines/validator_set/mod.rs

@@ -53,7 +53,7 @@ pub fn new_validator_set(spec: ValidatorSpec) -> Box<ValidatorSet> {
 }
 
 /// A validator set.
-pub trait ValidatorSet: Send + Sync {
+pub trait ValidatorSet: Send + Sync + 'static {
 	/// Get the default "Call" helper, for use in general operation.
 	// TODO [keorn]: this is a hack intended to migrate off of
 	// a strict dependency on state always being available.

ethcore/src/engines/validator_set/simple_list.rs

@@ -104,6 +104,12 @@ impl ValidatorSet for SimpleList {
 	}
 }
 
+impl AsRef<ValidatorSet> for SimpleList {
+    fn as_ref(&self) -> &ValidatorSet {
+        self
+    }
+}
+
 #[cfg(test)]
 mod tests {
 	use std::str::FromStr;