Ww3 feature/reduced credit

Added reduced scoring to WW3.  This includes:
* on the calendar, the reduced scoring dates appear and all dates can now be toggled. 
* everywhere where dates appears (Problem Sets Manager, Problem Details), there are fields for reduced scoring. 
* The global setting enable_reduced_scoring turns all reduced scoring on/off
* On a problem set, when the enable_reduced_scoring is toggled on/off, if there was no date before, it is now set based on a setting.