Switch to stock counterpart

We no longer need the custom counterpart. The things that were
changed in it and reasosn we no lomger need them are:

 1. set separator - this can be done with standard counterpart
 2. ES6 port: this was done to allow importing as _t, but is
    unnecessary with the _t wrapper function in react-sdk
    (although also seems to work fine with
    `import _t from 'counterpart';`)
 3. Fallback to key name: unnecessary with
    `setMissingEntryGenerator` in 0.18, but we've changed to just
    using a fallback locale anyway since No code missing en
    translations should ever make it to the devbelop branch.
 4. Logging on missing translations. Unnecessary with
    `onTranslationNotFound`, but now not used anyway because we
    let missing translations show up in the UI as
    'missing translation'

Bulk changes to imports coming in separate commit for easy reading.

package.json

@@ -50,7 +50,7 @@
     "browser-request": "^0.3.3",
     "classnames": "^2.1.2",
     "commonmark": "^0.27.0",
-    "counterpart-riot": "^0.18.1",
+    "counterpart": "^0.18.0",
     "draft-js": "^0.8.1",
     "draft-js-export-html": "^0.5.0",
     "draft-js-export-markdown": "^0.2.0",

src/languageHandler.js

@@ -1,5 +1,6 @@
 /*
 Copyright 2017 MTRNord and Cooperative EITA
+Copyright 2017 Vector Creations Ltd.
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
@@ -15,13 +16,27 @@ limitations under the License.
 */
 
 import request from 'browser-request';
-// Workaround for broken export
-import * as counterpart from 'counterpart-riot';
-import UserSettingsStore from './UserSettingsStore';
+import counterpart from 'counterpart';
 import q from 'q';
 
+import UserSettingsStore from './UserSettingsStore';
+
 const i18nFolder = 'i18n/';
 
+// We use english strings as keys, some of which contain full stops
+counterpart.setSeparator('|');
+// Fall back to English
+counterpart.setFallbackLocale('en');
+
+// The translation function. This is just a simple wrapper to counterpart,
+// but exists mostly because we must use the same counterpart instance
+// between modules (ie. here (react-sdk) and the app (riot-web), and if we
+// just import counterpart and use it directly, we end up using a different
+// instance.
+export function _t(...args) {
+    return counterpart.translate(...args);
+}
+
 export function setLanguage(languages, extCounterpart=null) {
     if (!languages || !Array.isArray(languages)) {
     const languages = this.getNormalizedLanguageKeys(this.getLanguageFromBrowser());