fix: display bounding box with different colors when predicting on multiple services

[alx]

Now that livedetect can use prediction on multiple deepdetect service, livedetect should be able to display the bounding boxes (or masks) from these services.

Currently, only bounding boxes from the last service prediction is displayed.

Bounding boxes from each service should have a distinct color, a qualitative color palette could be use to differentiate these services: http://colorbrewer2.org/#type=qualitative&scheme=Set1&n=9