Binance: Subscribe/unsubscribe response handling (#1444)

* Binance: Fix subscription failures ignored

* Testing: Fix race on shared config singleton

* Config: Privatise Global config var

We should *either* use a private var *or* use an accessor, but it
doesn't make sense to mix paradigms.
Since GetConfig() is well established this instead removes the limited uses of direct public access and adds a Setter

* Zip: Fix test failure on http mocks

testdata/configtest.json

@@ -495,7 +495,7 @@
         },
         "enabled": {
           "autoPairUpdates": true,
-          "websocketAPI": false
+          "websocketAPI": true
         }
       },
       "bankAccounts": [