add option to limit which coincs to follow-up with multiifos

[ahnitz]

No description provided.

[ahnitz]

This requires adding to the config file the following option.

--ifar-double-followup-threshold XXXX

Units in years like the standard ifar-upload-threshold option.
The option is required

[ahnitz]

@titodalcanton Ok, I think this works in my test in the sense that I see coincs above this threshold being output to xml files and below I see it in the hdf files with a 'NO_FOLLOWUP' key.

[tdent]

Does this need any further testing?

[titodalcanton]

No reason not to approve. The proof will be in the pudding.