update script/worker_analysis
update script/worker_analysis

allow marking worker as required (halt chain without it)
allow overriding run_order
allow disabling worker
extract variants config to variants key
remove extension of cache files
ramiroaraujo/image_optim,mihailim/image_optim,ramiroaraujo/image_optim,ramiroaraujo/image_optim,mihailim/image_optim,toy/image_optim,mihailim/image_optim,toy/image_optim,toy/image_optim