Chain-selection from UI (#4859)

* First little bits for chain-selection.

* Provide RPCs and get settings through to user defaults.

* Hasty stash.

* Fix updater accidentally redownloading.

* Finish up.

* Add JS tests.

* Hypervisor should never run a binary modified before itself.

* Style.

* Help tweak.

* Fix test compile.

* Fix JS test

* Build fix for tests.

* Revert default chain name

* Another test

* Use spec name via client.

* Fix mock up.

* whitespace

[ci:skip]

* whitespace

[ci:skip]

* remove exit/restart endpoints.

ethcore/src/client/config.rs

@@ -123,6 +123,8 @@ pub struct ClientConfig {
 	pub db_wal: bool,
 	/// Operating mode
 	pub mode: Mode,
+	/// The chain spec name
+	pub spec_name: String,
 	/// Type of block verifier used by client.
 	pub verifier_type: VerifierType,
 	/// State db cache-size.