Simplify and split config.json into defaultPreferences and buildConfig

src/common/config/buildConfig.js

@@ -0,0 +1,19 @@
+/**
+ * Build-time configuration. End-users can't change these parameters.
+ * @prop {Object[]} defaultTeams
+ * @prop {string} defaultTeams[].name - The tab name for default team.
+ * @prop {string} defaultTeams[].url - The URL for default team.
+ * @prop {string} helpLink - The URL for "Help->Learn More..." menu item.
+ *                           If null is specified, the menu disappears.
+ */
+const buildConfig = {
+  defaultTeams: [/*
+    {
+      name: 'example',
+      url: 'https://example.com'
+    }*/
+  ],
+  helpLink: 'https://docs.mattermost.com/help/apps/desktop-guide.html'
+};
+
+module.exports = buildConfig;