Delete code in VariableSpec.F90

[tclune]

This code in VariableSpec.F90:

      _SET_OPTIONAL(standard_name)
      _SET_OPTIONAL(itemtype)

      _SET_OPTIONAL(substate)
      _SET_OPTIONAL(service_items)
      _SET_OPTIONAL(default_value)
      _SET_OPTIONAL(vertical_dim_spec)
      _SET_OPTIONAL(attributes)
      _SET_OPTIONAL(bracket_size)
      _SET_OPTIONAL(dependencies)

should mostly be unnecessary now that everything uses StateItemAspect. But needs to be tested.