Add DownloadStatistics.__str__

Provides a summary of itself

csppfetch/__init__.py

@@ -105,6 +105,14 @@ class DownloadStatistics:
         self.deleted_files = 0
         self.deleted_size = 0
 
+    def __str__(self):
+        return (f"Downloaded {self.downloaded_files} files "
+            f"totalling {self.downloaded_size} bytes. "
+            f"Pulled {self.cache_hits} files from cache, "
+            f"saving {self.cache_size} bytes of download. "
+            f"Deleted {self.deleted_files} files, "
+            f"freeing {self.deleted_size} bytes of space. "
+            )
 
 
 def download_successful(state, dst, size, download_stats):