[ENH] make "Institutional department name" available for all datatypes

[Remi-Gau]

This PR is to keep in synch with changes on the validator and explicitly makes "Institutional department name" available for all modalities: it was included in the EEG and MEG json schema of the validator but not in the specs.

https://github.com/bids-standard/bids-validator/pull/1312

• simplify base definition of Institutional department name
• update MRI and PET definitions in macro calls
• add as metadata for EEG, MEG, iEEG
• add to behavior metadata (once [ENH] Make explicit that "task" metadata applies to "beh" modality #804 is merged)

[sappelhoff]

@Remi-Gau I just merged #804 - if you address the last point in your to do list, we can merge this PR as well.

[Remi-Gau]

@Remi-Gau I just merged #804 - if you address the last point in your to do list, we can merge this PR as well.

done

[sappelhoff]

Thanks again @Remi-Gau