JSON-RPC client generation (#2778)

* Bump jsonrpc & generate clients.

* Initial version of JSON-RPC client.

* Re-wort

* Remove spurious `#[derive(Encode, Decode)]`

They did not compile, since `Encode` and `Decode` are deliberately not
implemented for `usize`.

Fixes #2742.

* Re-write rpc-client example.

* Update to jsonrpc=12.0.0

* Remove unnecessary import

* Bump version.

* Revert version bump.

* Bump again.

substrate/core/rpc/src/author/hash.rs

@@ -14,13 +14,15 @@
 // You should have received a copy of the GNU General Public License
 // along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
 
+//! Extrinsic helpers for author RPC module.
+
 use primitives::Bytes;
-use serde::Deserialize;
+use serde::{Serialize, Deserialize};
 
 /// RPC Extrinsic or hash
 ///
 /// Allows to refer to extrinsic either by its raw representation or its hash.
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Serialize, Deserialize)]
 #[serde(rename_all = "camelCase")]
 pub enum ExtrinsicOrHash<Hash> {
 	/// The hash of the extrinsic.

substrate/core/rpc/src/author/mod.rs

@@ -16,6 +16,12 @@
 
 //! Substrate block-author/full-node API.
 
+pub mod error;
+pub mod hash;
+
+#[cfg(test)]
+mod tests;
+
 use std::sync::Arc;
 
 use client::{self, Client};
@@ -27,6 +33,7 @@ use log::warn;
 use parity_codec::{Encode, Decode};
 use primitives::{Bytes, Blake2Hasher, H256};
 use runtime_primitives::{generic, traits};
+use self::error::Result;
 use transaction_pool::{
 	txpool::{
 		ChainApi as PoolChainApi,
@@ -38,13 +45,7 @@ use transaction_pool::{
 	},
 };
 
-pub mod error;
-mod hash;
-
-#[cfg(test)]
-mod tests;
-
-use self::error::Result;
+pub use self::gen_client::Client as AuthorClient;
 
 /// Substrate authoring RPC API
 #[rpc]