The “launch” button should never be enabled if the audience is still under computation

To avoid activating a program too quickly and send to the wrong audience (eg, I update the smartlist but then quickly go to the control panel and activate the program before checking that the size of the audience seems correct), the activate button should be disabled until the calculation of the audience is completed. 

This safeguard goes in line with the other suggestion made here:

https://nation.marketo.com/t5/ideas/pop-up-alert-with-confirm-button-on-email-send-out/idi-p/312189