implemented run_background() for multi-electron simulations, moved common code to template.srw
implemented run_background() for multi-electron simulations, moved common code to template.srw

radiasoft/sirepo,mrakitin/sirepo,mkeilman/sirepo,mrakitin/sirepo,radiasoft/sirepo,mkeilman/sirepo,mkeilman/sirepo,mrakitin/sirepo,mkeilman/sirepo,radiasoft/sirepo,radiasoft/sirepo,radiasoft/sirepo,mrakitin/sirepo