update RecConf/Configuration.py in line with 2016/2017/2018 patches for pgun
In line with !2148 (merged) and !2149 (merged), update run2-patches rec configuration to not rely on explicit sequence setting in appconfig, as this is prone to breaking. Discovered when trying to set up productions for 2017 and 2018 pgun.
Edited by Marco Cattaneo