[dbirman]

BREAKING CHANGE: allow multiple subjects for acquisitions

1. Added support for multiple subjects and specimens, with separate procedures and acquisition details for each subject.
2. Added validators to keep subject groups consistent in each of the different core files
3. Updated asset inheritance rules to retain subject records when source subject sets match and remove them when the sets differ.
4. Changed subject and procedure files to JSON arrays and updated the core file writer API to support arrays.
5. Removed fixed asset-name formats and automatic name generation, so callers must supply asset names.

[saskiad]

I had a minor comment on naming convention (which is largely optional now so I'll approve as is, but check that out)