Add script to make monthly TEMP climatology file

POP looks for fields named "TEMPERATURE 1", "TEMPERATURE 2", ... "TEMPERATURE
12", so I included a SourceMod to add a leading 0 to 1-digit months
("TEMPERATURE01" and so on); the gen_pt_dataset.ncl script takes monthly
climatology data from the TEMP field in a file provided by Steve Y and creates
a new file with the proper file name.