Bitfinex: Fix websocket trade processing (#1754)

* Bitfinex: Fix WS trade processing

* Add handling for funding trades

Fixes #1746

* Linter: Disable shadow linting for err

It's been a year, and I'm still getting caught out by govet demanding I
don't shadow a var I was deliberately shadowing.
Made worse by an increase in clashes with stylecheck when they both want
opposite things on the same line.

* Bitfinex: Move websocket constants to websocket file

* Bitfinex: Rename channel consts

* Bitfinex: Send individual WS trades down the DataHandler

testdata/configtest.json

@@ -643,7 +643,8 @@
     },
     "enabled": {
      "autoPairUpdates": true,
-     "websocketAPI": true
+     "websocketAPI": true,
+     "tradeFeed": true
     }
    },
    "bankAccounts": [