Support for extra_files in structured_data for smaht-submitr

[dmichaels-harvard]

• TODO: Actually not doing extra-files support for now; will back out these changes;
  but same branch for some smaht-submitr validation/submission progress tracking.
• Support for ExtraFiles pseudo-type, to handle extra_files in smaht-submitr..
• Minor structured_data fix related to counting unresolved references;
  not functionally consequential; only incorrect user feedback in smaht-submitr.
• Minor changes to support smaht-submitr validation/submission progress tracking.

[coveralls]

Pull Request Test Coverage Report for Build 8559549681

Details

• 111 of 143 (77.62%) changed or added relevant lines in 5 files are covered.
• 5 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.1%) to 77.279%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
dcicutils/portal_object_utils.py	4	6	66.67%
dcicutils/submitr/progress_constants.py	64	67	95.52%
dcicutils/data_readers.py	1	5	20.0%
dcicutils/structured_data.py	35	58	60.34%

Files with Coverage Reduction	New Missed Lines	%
dcicutils/data_readers.py	1	83.92%
dcicutils/structured_data.py	4	70.51%

Totals
Change from base Build 8269652579:	0.1%
Covered Lines:	10925
Relevant Lines:	14137

---

💛 - Coveralls