title: QDoubleValidator accepts multiple decimal points
body: <p>I'm using a <code>QDoubleValidator</code> for my <code>QLineEdit</code>. The application locale (set in QtCreator) is <code>QLocale::German</code>.</p>
  
  <p>Now when I enter a valid double (either using a dot or a comma as decimal separator) writing to the textedit as well as converting the string to a float works perfectly fine. But the validator also lets me write stuff with multiple decimal separators. Strings like <code>123.567,890</code> or <code>,,03.4...</code> get validated but can't get converted into a float.</p>
  
  <p>Is there a way to tell <code>QDoubleValidator</code> to only validate <strong>real</strong> numbers and not just strings without alphabetical characters?</p>
  
  <p>I basically want to have a validator, that only validates strings, that can get converted to floats
  using either the default locale or the german locale.</p>