Slight change to debug output
Simplified isTraced method
Hist now only keeps points for objects when conf was calculated

Previously, there was an assumption that Hist was able to use information about objects (e.g. position) whenever they were visible. However, this is unrealistic. Objects should only have their history tracked during time steps when their confidence is calculated (i.e. the camera already uses resources scanning for the object). This is now the case, meaning that there is no overhead to using Hist compared with a non-Hist node.