A few changes on Public and Admin interface

Created by: DBinaghi

Hi. I've been playing around a bit with the plugin, and added a few new features. Mainly, now plugin checks whether there're only Item Types or Metadata selected, or both, and then changes navigation titles accordingly. Besides, added an option to show/hide references count. Finally, fixed some problems with UTF-8 and labels (you might want to check whether you want to keep the extended alphabet I've added in reference-list.php, or you want to rever to the shorter English one... it might be interesting to add letters for other alphabets, or a config option to choose alphabet).