Allow sorting by number of appearanes in code

[Toranks]

To partially translate some programs with large amounts of text, it would sometimes be useful to be able to sort by the number of occurrences of a string, as one more way of filtering out which are the most common strings, and translate them first.

[vslavik]

Sorry, I'm going to say no to this. Heavily reused strings are exceedingly rare and if they're present, it's something easily handled with a single pre-translation pass.