Step labels

[mkomarsr]

This is more of a feature request but here we are.

Currently, we can use:

      popup_yes_step: 10 
      popup_no_step: 5 

To skip forward and backward to a specific numbered step. It would be very nice to be able to label a step using something like:

step_label: before_probe

and then something like.

      popup_yes_step: before_probe
      popup_no_step: full_send