added pass through of threshold for recon

[ALEXJAZZ008008]

No description provided.

[KrisThielemans]

looks good. Can you add some doc? (hopefully can steal it from STIR) Ideally add it to MATLAB but you might not be able to test that, in which case it's a bad idea.

@evgueni-ovtchinnikov, how do you keep track of what features still need to be ported to MATLAB?

@ALEXJAZZ008008 please add a line in CHANGES.md

[KrisThielemans]

@ALEXJAZZ008008 could you give this a quick look such that we can merge it in before 2.2? Should only take 5 mins to add in the doc. I don't see why this PR should be updating the data submodule though. As that's rather fragile, I'd vastly prefer if it doesn't.

[ALEXJAZZ008008]

Yes, I'll look at this first thing tomorrow.
I agree that there shouldn't be changes to data I believe this will be because I used "got add ."