Add NFP for ScheduleRuleset

[kbenne]

Pull request overview

This PR adds the NFP design document for native Schedule:Ruleset support in EnergyPlus.

[kbenne]

A key comment from team discussion was around how date/time is expressed in the input. @joseph-robertson please review and facilitate discussion and possible revisions to the design.

[joseph-robertson]

I believe one of the comments/suggestions was to consider revising the Date Specification Type (currently either DateRange or SpecificDates). Specifically, to offer one date specification type along the lines of extensible date ranges. Something like:

  N2 , \field Start Month <x>
       \begin-extensible
       \type integer
       \minimum 1
       \maximum 12
       \default 1
  N3 , \field Start Day <x>
       \type integer
       \minimum 1
       \maximum 31
       \default 1
  N4 , \field End Month <x>
       \type integer
       \minimum 1
       \maximum 12
       \default 12
  N5 , \field End Day <x>
       \type integer
       \minimum 1
       \maximum 31
       \default 31