fileystem: Use human-readable ADF name if available.

When using __str__ for a CardDF we would get "DF(DF.TELECOM)"
but when using it on CardADF we would get ADF(a0000000871002)"
instead of "ADF(ADF.USIM)".  Let's fix that.

Change-Id: I5801a08bcc28cb222734af6d9ee835227f4fee69

pySim/filesystem.py

@@ -488,7 +488,7 @@ class CardADF(CardDF):
             mf.add_application_df(self)
 
     def __str__(self):
-        return "ADF(%s)" % (self.aid)
+        return "ADF(%s)" % (self.name if self.name else self.aid)
 
     def _path_element(self, prefer_name: bool):
         if self.name and prefer_name: