apply Horizon masking to postprocessing

[greenLeopard]

Precondition:
smoke detection has been applied to an image, and
at least one sub-image has P(smoke) > threshold

Process:
apply horizon mask to the original image
exclude sub-images with P(smoke) > threshold if it is above the horizon
Definition of done:
return a list indicating which of the sub-images are included and excluded after horizon masking