Initial: Offchain Workers (#1942)

* Refactor state-machine stuff.

* Fix tests.

* WiP

* WiP2

* Service support for offchain workers.

* Service support for offchain workers.

* Testing offchain worker.

* Initial version working.

* Pass side effects in call.

* Pass OffchainExt in context.

* Submit extrinsics to the pool.

* Support inherents.

* Insert to inherents pool.

* Inserting to the pool asynchronously.

* Add test to offchain worker.

* Implement convenience syntax for modules.

* Dispatching offchain worker through executive.

* Fix offchain test.

* Remove offchain worker from timestamp.

* Update Cargo.lock.

* Address review comments.

* Use latest patch version for futures.

* Add CLI parameter for offchain worker.

* Fix compilation.

* Fix test.

* Fix extrinsics format for tests.

* Fix RPC test.

* Bump spec version.

* Fix executive.

* Fix support macro.

* Address grumbles.

* Bump runtime

substrate/core/sr-primitives/src/lib.rs

@@ -393,21 +393,6 @@ impl From<sr25519::Signature> for AnySignature {
 	}
 }
 
-/// Context for executing a call into the runtime.
-#[derive(Copy, Clone, Eq, PartialEq, Encode, Decode)]
-#[cfg_attr(feature = "std", derive(Debug, Serialize))]
-#[repr(u8)]
-pub enum ExecutionContext {
-	/// Context for general importing (including own blocks).
-	Importing,
-	/// Context used when syncing the blockchain.
-	Syncing,
-	/// Context used for block construction.
-	BlockConstruction,
-	/// Context used for other calls.
-	Other,
-}
-
 #[derive(Eq, PartialEq, Clone, Copy, Decode)]
 #[cfg_attr(feature = "std", derive(Debug, Serialize))]
 #[repr(u8)]