Only back up changed files

We only need to back up files with a score != 0 and count != 0

libsaria/path/backup.py

@@ -34,6 +34,8 @@ def decode_attr(attr):
 
 def encode_track(doc, node, id):
 	filepath, score, count = get_attrs(id, "filepath", "score", "count")
+	if score == 0 and count == 0:
+		return
 	child = add_child(doc, node, "track", {"score":score, "count":count})
 	add_text(doc, child, filepath)