Following @rafael advice on a related commit to slaprunner

    nexedi/slapos@c8c81baa
    nexedi/slapos!22 (comment 1780)

let's also leverage multicore when building NumPy- & Ruby- related
software under testnodes.

/reviewed-by @rafael, @seb  (on !23)

it can be used as both portal type action and workflow action.

also add 'Declare as Delivered' transition so that the created event can become directly delivered state.