title: Batch lowercase of text files content
body: <p>After half an hour searching for an answer to this, I can't think of a way to do it (without it involving opening each text file individually, selecting all and then lowercase-ing with gedit. I would like to be able to run a script, be it by commandline or preferably to include into nautilus-scripts, so that if I select the files on the GUI and rightclick to scripts and lowercase and it will be done.
   I know that tr is able to know how to do it, but I can't figure out how can I turn the following call to  <code>tr '[:upper:]' '[:lower:]' &lt; input.txt &gt; output.txt</code> Normally, I would change input.txt to *.txt and *.txt for output.txt, but it doesn't work. Any ideas?</p>
  
  <p>Extra: once that is solved, how to adapt it for nautilus-scripts? :]</p>
  
  <p>Thanks!</p>