Provide the number of models using the .size member for the file parameters...

Provide the number of models using the .size member for the file parameters handler, similarly to the grid parameters handler.

pcigale/handlers/parameters_handler.py

@@ -152,6 +152,8 @@ class ParametersHandlerFile(object):
         table = read_table(configuration['parameters_file'])
         table.sort(table.colnames)
 
+        self.size = len(table)
+
         self.modules = []
         for colname in table.colnames:
             module = colname.split('.', 1)[0]