tumbnail export buggy

thumbnail export is not consistent in its output when using the "-p" switch to read frame data against a profile. Specifically, it seems to prioritize the most-triggered threshold, typically VREP, at the expense of everything else.

At this time it is recommended that users looking for thumbnail exports use the single tag mode.

The problem is likely in the handling of thumbExportDelay. First proposed solution is to create a dictionary with keys for each tag, and track thumb export delays for each tag.