title: Change file type association in PyCharm
body: <p>I have a file in PyCharm and its used to be just a <code>.txt</code> file.
  Now I wanted to use <code>.rst</code> (reStructuredText).</p>
  <p>I know that when I open a file without an ending for the first time PyCharm asks me what kind of file it is and how the syntax should therefore be interpreted.</p>
  <p>Can I open up that dialog again somehow, or can I change the association in some other way?</p>