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.

js/src/api/rpc/parity/parity.js

@@ -284,9 +284,15 @@ export default class Parity {
       .execute('parity_mode');
   }
 
+  // DEPRECATED - use chain instead.
   netChain () {
     return this._transport
-      .execute('parity_netChain');
+      .execute('parity_chain');
+  }
+
+  chain () {
+    return this._transport
+      .execute('parity_chain');
   }
 
   netPeers () {
@@ -454,6 +460,11 @@ export default class Parity {
       .execute('parity_setMode', mode);
   }
 
+  setChain (specName) {
+    return this._transport
+      .execute('parity_setChain', specName);
+  }
+
   setNewDappsAddresses (addresses) {
     return this._transport
       .execute('parity_setNewDappsAddresses', addresses ? inAddresses(addresses) : null);