renamed mirror element to "Flat Mirror", implemented mirror upload/download with errors
renamed mirror element to "Flat Mirror", implemented mirror upload/download with errors

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