Permit nchs-mortality to publish to Epidata off-cycle

[krivard]

The first update for a new epiweek from NCHS typically occurs before the nchs-mortality indicator is scheduled on Mondays, but is occasionally delayed (twice in the last 3 months). Since the nchs-mortality indicator only publishes to Epidata once a week, a delayed update means the maximum minimum lag grows to 22 days instead of the usual max of 15 days over the course of a week:

Monday publishing to Epidata is hard-coded in the nchs-mortality indicator. If we were able to selectively configure the indicator to force a publish using the params file irrespective of the day of the week, we could react to delayed deliveries from NCHS with a one-off run of the indicator in publish mode. This would limit the maximum minimum lag growth in these circumstances to 16 days.

This change requires:

• adding an optional parameter to the indicator section of params.json
• adding handling code in run.py
• adding a test to make sure that epidata publishing occurs on a non-Monday when force publish is set in params