Add motif list column to AME output

[snystrom]

This should be kept consistent. Or at least, I need some feedback on how to deal with this. What I don't like is when people show plots of the PWM with a p-value as if it's denovo. But perhaps only having a motif column won't encourage that behavior. Folks should certainly be able to evaluate the motif that is enriched to determine if it is a high quality matrix, etc.