Minor fix in structured_data to not try to resolve empty refs.

[dmichaels-harvard]

• Minor fix in structured_data to not try to resolve empty refs in norefs mode; and added StructuredDataSet.unchecked_refs; not functionally substantive as used (only) with smaht-submitr/submit-metadata-bundle --info --refs.
• Added nrows and nsheets to data_reader; convenience for smaht-submitr/submit-metadata-bundle --info.
• Added test_progress_bar module for progress_bar testing; would like to add more tests.
• Fixed up captured_output module to handle UTF-8 encoding to help unit testing progress_bar.
• Added hooks to progress_bar to help unit testing.
• Added a find_nth_from_end and set_nth to misc_utils to help progress_bar unit testing.
• Added format_size and format_duration misc_utils; refactor from smaht-submitr.
• Added format_datetime, parse_datetime to datetime_utils; refactor from smaht-submitr; and some tests.
• Added check_only flag to portal_utils.Portal.{post,patch}_metadata (came up in ad hoc troubleshooting).

[coveralls]

Pull Request Test Coverage Report for Build 8775064413

Details

• 182 of 306 (59.48%) changed or added relevant lines in 7 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage increased (+0.6%) to 76.867%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
dcicutils/portal_utils.py	2	6	33.33%
dcicutils/data_readers.py	4	9	44.44%
dcicutils/captured_output.py	0	16	0.0%
dcicutils/progress_bar.py	74	90	82.22%
dcicutils/structured_data.py	2	18	11.11%
dcicutils/datetime_utils.py	88	118	74.58%
dcicutils/misc_utils.py	12	49	24.49%
<!--	Total:	182	306	59.48%	-->

Files with Coverage Reduction	New Missed Lines	%
dcicutils/structured_data.py	1	69.36%
<!--	Total:	1		-->

Totals
Change from base Build 8664068591:	0.6%
Covered Lines:	11221
Relevant Lines:	14598

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💛 - Coveralls