ValidatorSet reporting (#4208)

* remove register_account_provider

* build rpc module

* new dummy client

* common EngineSigner struct

* from -> into

* initial report via call

* separate safe from regular contract

* transact_contract

* fix build

* return Signature, docs

* add sign method to some engines

* add safeContract spec

* update specs to new contracts

* use AuthorityRound for contract spec

* add more reporting

* add reporting test

* use gas floor

* shorter

ethcore/src/error.rs

@@ -26,6 +26,7 @@ use types::block_import_error::BlockImportError;
 use snapshot::Error as SnapshotError;
 use engines::EngineError;
 use ethkey::Error as EthkeyError;
+use account_provider::Error as AccountsError;
 
 pub use types::executed::{ExecutionError, CallError};
 
@@ -265,6 +266,8 @@ pub enum Error {
 	Engine(EngineError),
 	/// Ethkey error.
 	Ethkey(EthkeyError),
+	/// Account Provider error.
+	AccountProvider(AccountsError),
 }
 
 impl fmt::Display for Error {
@@ -287,6 +290,7 @@ impl fmt::Display for Error {
 			Error::Snapshot(ref err) => err.fmt(f),
 			Error::Engine(ref err) => err.fmt(f),
 			Error::Ethkey(ref err) => err.fmt(f),
+			Error::AccountProvider(ref err) => err.fmt(f),
 		}
 	}
 }
@@ -396,6 +400,12 @@ impl From<EthkeyError> for Error {
 	}
 }
 
+impl From<AccountsError> for Error {
+	fn from(err: AccountsError) -> Error {
+		Error::AccountProvider(err)
+	}
+}
+
 impl<E> From<Box<E>> for Error where Error: From<E> {
 	fn from(err: Box<E>) -> Error {
 		Error::from(*err)