findChangeLog: don't crash if sort is unspecified

This would crash:

    api.findChangeLogs(keys=[])

because there's no 'name' key for changelog entries. Instead, default to
chronological order, newest first.

pandora/changelog/views.py

@@ -18,7 +18,7 @@ import models
 def parse_query(data, user):
     query = {}
     query['range'] = [0, 100]
-    query['sort'] = [{'key':'name', 'operator':'+'}]
+    query['sort'] = [{'key':'created', 'operator':'-'}]
     for key in ('keys', 'group', 'list', 'range', 'sort', 'query'):
         if key in data:
             query[key] = data[key]