Made it possible to override translations via theme system

app/Config/app.php

@@ -96,7 +96,6 @@ return [
         Illuminate\Redis\RedisServiceProvider::class,
         Illuminate\Auth\Passwords\PasswordResetServiceProvider::class,
         Illuminate\Session\SessionServiceProvider::class,
-        Illuminate\Translation\TranslationServiceProvider::class,
         Illuminate\Validation\ValidationServiceProvider::class,
         Illuminate\View\ViewServiceProvider::class,
         Illuminate\Notifications\NotificationServiceProvider::class,
@@ -107,9 +106,9 @@ return [
         Barryvdh\DomPDF\ServiceProvider::class,
         Barryvdh\Snappy\ServiceProvider::class,
 
-
         // BookStack replacement service providers (Extends Laravel)
         BookStack\Providers\PaginationServiceProvider::class,
+        BookStack\Providers\TranslationServiceProvider::class,
 
         // BookStack custom service providers
         BookStack\Providers\AuthServiceProvider::class,

app/Providers/TranslationServiceProvider.php

@@ -0,0 +1,21 @@
+<?php namespace BookStack\Providers;
+
+use BookStack\Translation\FileLoader;
+use Illuminate\Translation\TranslationServiceProvider as BaseProvider;
+
+class TranslationServiceProvider extends BaseProvider
+{
+
+    /**
+     * Register the translation line loader.
+     * Overrides the default register action from Laravel so a custom loader can be used.
+     * @return void
+     */
+    protected function registerLoader()
+    {
+        $this->app->singleton('translation.loader', function ($app) {
+            return new FileLoader($app['files'], $app['path.lang']);
+        });
+    }
+
+}

app/Translation/FileLoader.php

@@ -0,0 +1,30 @@
+<?php namespace BookStack\Translation;
+
+use Illuminate\Translation\FileLoader as BaseLoader;
+
+class FileLoader extends BaseLoader
+{
+    /**
+     * Load the messages for the given locale.
+     * Extends Laravel's translation FileLoader to look in multiple directories
+     * so that we can load in translation overrides from the theme file if wanted.
+     * @param  string  $locale
+     * @param  string  $group
+     * @param  string|null  $namespace
+     * @return array
+     */
+    public function load($locale, $group, $namespace = null)
+    {
+        if ($group === '*' && $namespace === '*') {
+            return $this->loadJsonPaths($locale);
+        }
+
+        if (is_null($namespace) || $namespace === '*') {
+            $themeTranslations = $this->loadPath(theme_path('lang'), $locale, $group);
+            $originalTranslations =  $this->loadPath($this->path, $locale, $group);
+            return array_merge($originalTranslations, $themeTranslations);
+        }
+
+        return $this->loadNamespaced($locale, $group, $namespace);
+    }
+}