Flatten GUI tree somewhat

The very deep tree structure didn't really aggree with me, sorry. This
makes the core module rather large, but on the other hand that just
highlights that it is rather large.

gui/syncthing/core/languageSelectDirective.js

@@ -0,0 +1,48 @@
+angular.module('syncthing.core')
+    .directive('languageSelect', function (LocaleService) {
+        'use strict';
+        return {
+            restrict: 'EA',
+            template:
+                    '<a ng-if="visible" href="#" class="dropdown-toggle" data-toggle="dropdown" aria-expanded="true"><span class="glyphicon glyphicon-globe"></span>&nbsp;{{localesNames[currentLocale] || "English"}} <span class="caret"></span></a>'+
+                    '<ul ng-if="visible" class="dropdown-menu">'+
+                        '<li ng-repeat="(i,name) in localesNames" ng-class="{active: i==currentLocale}">'+
+                            '<a href="#" data-ng-click="changeLanguage(i)">{{name}}</a>'+
+                        '</li>'+
+                    '</ul>',
+
+            link: function ($scope) {
+                var availableLocales = LocaleService.getAvailableLocales();
+                var localeNames = LocaleService.getLocalesDisplayNames();
+                var availableLocaleNames = {};
+
+                // get only locale names that present in available locales
+                for (var i = 0; i < availableLocales.length; i++) {
+                    var a = availableLocales[i];
+                    if (localeNames[a]) {
+                        availableLocaleNames[a] = localeNames[a];
+                    } else {
+                        // show code lang if it is not in the dict
+                        availableLocaleNames[a] = '[' + a + ']';
+                    }
+                }
+
+                $scope.localesNames = availableLocaleNames;
+                $scope.visible = $scope.localesNames && $scope.localesNames['en'];
+
+                // using $watch cause LocaleService.currentLocale will be change after receive async query accepted-languages
+                // in LocaleService.readBrowserLocales
+                var remove_watch = $scope.$watch(LocaleService.getCurrentLocale, function (newValue) {
+                    if (newValue) {
+                        $scope.currentLocale = newValue;
+                        remove_watch();
+                    }
+                });
+
+                $scope.changeLanguage = function (locale) {
+                    LocaleService.useLocale(locale, true);
+                    $scope.currentLocale = locale;
+                };
+            }
+        };
+    });