A driver command that will try to completely unload all product from the train.
The unload is repeated some number of times and there is a delay between each unload.
The string-table has five tags to specify the labels and values for the number of
times to repeat the unload process. They are 'unload_x_label' and 'unload_x_val',
respectivaly, where the x is an integer from 0 upto 4.
Between each unload there will be a delay in seconds. The labels and the number of
seconds can be specified with the tags 'delay_x_label' and 'delay_x_val', respectively,
where the x stands for an integer from 0 upto 9.