time_series extraction changed fid to numeric for a better sorting in the csv output

sen2chain/time_series.py

@@ -393,6 +393,7 @@ class TimeSeries:
                 self._date_min,
                 self._date_max)
             #~ df.sort_values(by=['fid', 'date', 'count', 'tile']).reindex(columns=(list_order + [a for a in df.columns if a not in list_order]), copy=False).to_csv(str(csv_path))
+            df['fid'] = pd.to_numeric(df['fid'])
             dg = df.sort_values(by=['fid', 'date', 'count', 'std'], ascending=[True, True, True, False]).\
                     reindex(columns=(list_order + [a for a in df.columns if a not in list_order]), copy=False).\
                     reset_index().\