Verbose reporting could be improved

[dkp]

Use case: I have a subject with several sessions, only one session, ctbspre, actually has dwi data. However, when I run intend4, it reports that it has modified 6 epi sidecars

dpat@saci data % intend4.sh dwi --participant-label 163
(intend4): Modifying IntendedFor field in sidecar files for modality 'dwi'.
(intend4): Processing subject 163 in session itbspre
(intend4): Processing subject 163 in session ctbspost
(intend4): Processing subject 163 in session itbspost
(intend4): Processing subject 163 in session ctbspre
(intend4): Processing subject 163 in session shampost
(intend4): Processing subject 163 in session shampre
(intend4): Modified IntendedFor fields in 6 epi sidecars.