Fix question reference in InstrumentToWarehouse spec.

The integrity checks added in f7679287f9378da7eab0efc608a349ad79b8 to
address #4084 make this necessary.  (That's a good thing.)

This is part of
https://code.bioinformatics.northwestern.edu/issues/issues/show/4379.
(cherry picked from commit 6f36ee1b86cabf2c19fe12801b788d407da038da)
Implement MDES time and date coding.

Related to
https://code.bioinformatics.northwestern.edu/issues/issues/show/4379.
(cherry picked from commit 0773371ab1d390d0f1e9fba7053e9d127c4fab9d)
Merge pull request #235 from NUBIC/task-4379-mdes-datetime-coding-for-1.6.x

Export answers of -1, -2, etc. as MDES-coded dates / times (1.6.x)