Adding image pagination

Add image pagination component so that multiple images can be cycled through without fetching them all. This is useful for loading analysis images for each template bank bin, for example, the horizon history and the background SNR_Chi^2 PDF from the ranking statistics.

Note: this should not cause any backward compatibility problem since it only adds new feature.

Demo: https://ldas-jobs.ligo.caltech.edu/~chiwai.chan/image_pagintation/

mentioned in commit lscsoft/gstlal@cd7f37a6

mentioned in merge request lscsoft/gstlal!114 (merged)

changed the description

Looks good to me, thanks!

approved this merge request

merged

mentioned in commit lscsoft/gstlal@d287253a

mentioned in commit lscsoft/gstlal@5eacc561