title: add new voices to freeTTS other than us voices
body: <p>I am working on a speech recognition project, therefore I need to have audio files for more than thousands of words. I have done everything correctly in order to use <code>Mbrola</code> voices in <code>FreeTTS</code> but I can only use <code>us1,us2,us3</code>. It doesn't 
  recognize any other voices. </p>
  
  <p>When I try to use <code>mbrola_en1</code> I get this error:</p>
  
  <blockquote>
    <p>Invalid Voice: Mbrola_en1<br>
        valid voices: alan kevin kevin16 mbrola_us1 mbrola_us2 mbrola_us3</p>
  </blockquote>
  
  <p>I read all the questions related to this but unfortunately none of them are answered.</p>
  
  <p>Does anyone know how to fix this issue?</p>