RPC & Client (#21)

* Initial version of http server.

* Refactor the structure.

* add unassigned ports info.

* Rename servers to match conventions.

* Add client crate and some proper RPC implementations.

* Style & docs.

substrate/state_machine/src/lib.rs

@@ -162,7 +162,7 @@ pub trait Error: 'static + fmt::Debug + fmt::Display + Send {}
 impl<E> Error for E where E: 'static + fmt::Debug + fmt::Display + Send {}
 
 /// Externalities: pinned to specific active address.
-pub trait Externalities<Executor>: StaticExternalities<Executor> {
+pub trait Externalities<CodeExecutor>: StaticExternalities<CodeExecutor> {
 	/// Read storage of current contract being called.
 	fn storage(&self, key: &H256) -> Result<&[u8], Self::Error> {
 		StaticExternalities::storage(self, key)
@@ -181,7 +181,7 @@ pub trait Externalities<Executor>: StaticExternalities<Executor> {
 }
 
 /// Static externalities: used only for read-only requests.
-pub trait StaticExternalities<Executor> {
+pub trait StaticExternalities<CodeExecutor> {
 	/// Externalities error type.
 	type Error: Error;
 
@@ -193,7 +193,7 @@ pub trait StaticExternalities<Executor> {
 }
 
 /// Contract code executor.
-pub trait Executor: Sized {
+pub trait CodeExecutor: Sized {
 	/// Error type for contract execution.
 	type Error: Error;
 
@@ -220,7 +220,7 @@ pub trait Executor: Sized {
 /// Execute a call using the given state backend, overlayed changes, and call executor.
 ///
 /// On an error, no prospective changes are written to the overlay.
-pub fn execute<B: backend::Backend, Exec: Executor>(
+pub fn execute<B: backend::Backend, Exec: CodeExecutor>(
 	backend: &B,
 	overlay: &mut OverlayedChanges,
 	exec: &Exec,