fixed the made-up word "authentification", also changed the title of that dialog to "Pass Phrase", dialog message then only contains the key details or "Symmetric encryption."

Update issue 39
I tried to change "title_athentication", "passPhraseForSymmetricEncryption", and "passPhraseFor" in all languages. I think the changes are correct, but if you guys could make sure I didn't do anything dumb, then that'd be better. :)

src/org/thialfihar/android/apg/AskForSecretKeyPassPhrase.java

@@ -40,7 +40,7 @@ public class AskForSecretKeyPassPhrase {
                                       PassPhraseCallbackInterface callback) {
         AlertDialog.Builder alert = new AlertDialog.Builder(context);
 
-        alert.setTitle(R.string.title_authentification);
+        alert.setTitle(R.string.title_authentication);
 
         final PGPSecretKey secretKey;
         final Activity activity = context;