Improve OS menu (#1563)

* Remove reload options, new file/help menus, tools/log at bottom

* Further menus refactor: install handlers at template creation

* WIP: Further tune menus, add custom about window

* New About window, new help menu items, menu labels now i18n

* Default device name on registration is now computer hostname

The OS of the device makes sense for those of us testing across a lot of
different OSes. And maybe for a user with just one desktop device. But
most users with multiple desktop devices are using the same OS for both.

* About window: Only show window when content is ready

* Fix typo in app/menu.js

js/views/install_view.js

@@ -45,13 +45,7 @@
 
             var deviceName = textsecure.storage.user.getDeviceName();
             if (!deviceName) {
-                if (navigator.userAgent.match('Mac OS')) {
-                    deviceName = 'Mac';
-                } else if (navigator.userAgent.match('Linux')) {
-                    deviceName = 'Linux';
-                } else if (navigator.userAgent.match('Windows')) {
-                    deviceName = 'Windows';
-                }
+                deviceName = window.config.hostname;
             }
 
             this.$('#device-name').val(deviceName);