[thing] deClump/pyDeClump.findClumps - missing doc, questionable gap parameter? #933

Describe the bug
see tests PR'd in #932. deClump and pyDeClump have differing behavior, and neither seem to work with nFrame=0, (i.e. no gap, clumping on the same frame only)

To Reproduce
Steps to reproduce the behavior:

1. Go to add declump tests following pyDeClump doc #932
2. pull or copy paste
3. See error

Expected behavior
I thought I could use this to group localizations that only appear on the same frame