Add Serbian translation and update translations

UI/MainUI/English.lproj/Localizable.strings

@@ -11,7 +11,7 @@
 "Authenticating" = "Authenticating";
 
 /* Appears when authentication succeeds */
-"Success" = "Success";
+"Welcome" = "Welcome";
 
 "Authentication Failed" = "Authentication Failed";
 "Wrong username or password." = "Wrong username or password.";
@@ -45,6 +45,7 @@
 "Portuguese" = "Português";
 "BrazilianPortuguese" = "Português brasileiro";
 "Russian" = "Русский";
+"Serbian" = "Српски";
 "Slovak" = "Slovensky";
 "Slovenian" = "Slovenščina";
 "SpanishSpain" = "Español (España)";
@@ -53,6 +54,7 @@
 "TurkishTurkey" = "Türkçe (Türkiye)";
 "Ukrainian" = "Українська";
 "Welsh" = "Cymraeg";
+
 "About" = "About";
 "AboutBox" = "Developed by Inverse, SOGo is a fully-featured groupware server with a focus on scalability and simplicity.<br/><br/>
 SOGo provides a rich AJAX-based Web interface and supports multiple native clients through the use of standard protocols such as CalDAV and CardDAV.<br/><br/>