implemented background task for multi-electron simulations, share code with cli.srw
implemented background task for multi-electron simulations, share code with cli.srw

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