split HDD_id into individual explicit variables

[sunt05]

      ! TODO: split HDD_id into individual explicit variables

https://github.com/UMEP-dev/SUEWS/blob/2d6b87fd785cf1037b028ed01f7416dfb7068722/src/suews/src/suews_ctrl_type.f95#L458

! HDD_id:
      ! first half used for update through the day
      ! HDD_id(1) ---- Heating [degC]: used for accumulation during calculation
      ! HDD_id(2) ---- Cooling [degC]: used for accumulation during calculation
      ! HDD_id(3) ---- Daily mean temp [degC]: used for accumulation during calculation
      ! HDD_id(4) ---- 5-day running mean temp [degC]: used for actual calculation
      ! HDD_id(5) ---- Daily precip total [mm]
      ! HDD_id(6) ---- Days since rain [d]
      ! second half used for storage of the first half for the prevous day
      ! HDD_id(6+1) ---- Heating [degC]: used for accumulation during calculation
      ! HDD_id(6+2) ---- Cooling [degC]: used for accumulation during calculation
      ! HDD_id(6+3) ---- Daily mean temp [degC]: used for accumulation during calculation
      ! HDD_id(6+4) ---- 5-day running mean temp [degC]: used for actual calculation
      ! HDD_id(6+5) ---- Daily precip total [mm]
      ! HDD_id(6+6) ---- Days since rain [d]

[sunt05]

being addressed in #166