Language selection combobox in options and accepted languages.

Added language selection combobox in options dialog. Selecting
language here will overwrite language code gathered from system.

Added AcceptedLanguages map to Translator, which holds readable
names and lang-country codes with avaailable languages. Filled
it with languages in which URTrator already translated. Francais
coming :)

translator/translator_unix.go

@@ -73,6 +73,7 @@ func (t *Translator) detectTranslationsDirectory() error {
         if err != nil {
             t.Language = "en_US"
             fmt.Println("Translations unavailable, forcing en_US language code")
+            return errors.New("No translations directory was detected!")
         } else {
             t.translationsPath = "/usr/share/urtrator/translations"
         }
@@ -80,11 +81,5 @@ func (t *Translator) detectTranslationsDirectory() error {
         t.translationsPath = translations_dir
     }
 
-    if t.translationsPath != "" {
-        t.translationsPath = filepath.Join(t.translationsPath, t.Language)
-    } else {
-        return errors.New("No translations directory was detected!")
-    }
-
     return nil
 }