Feature 1753 python_fill

[JohnHalleyGotway]

Pull Request Testing

• Describe testing already performed for these changes:
  
  Tested the python script from @j-opatz on kiowa to confirm that it was broken but is now fixed. Here's log output from the tests which shows the correct max value now.

cd /d1/personal/johnhg/MET/MET_Help/opatz_data_20210415
./run_pdp.sh
DEBUG 1: Opening data file: PYTHON_NUMPY
DEBUG 4: Met2dDataFileFactory::new_met_2d_data_file() -> created new Met2dDataFile object of type "FileType_Python_Numpy".
DEBUG 4: VarInfoFactory::new_var_info() -> created new VarInfo object of type "FileType_Python_Numpy".
DEBUG 3: Calling /usr/local/python3/bin/python3 to run user's python script (./poe_fcst_embedded).
DEBUG 4: Writing temporary Python dataplane file:
DEBUG 4: 	/usr/local/python3/bin/python3 /d1/personal/johnhg/MET/MET_Help/opatz_data_20210415/MET-feature_1753_python_fill/met/share/met/wrappers/write_tmp_dataplane.py /tmp/tmp_met_nc_36314_0 ./poe_fcst_embedded /d1/projects/CPC_data/input/precip_poe_fcsts/2019/08/07/gefs-legacy-00z_rfcst-cal_precip_20190807_week2.nc:33
...
DEBUG 4: Reading temporary Python dataplane file: /tmp/tmp_met_nc_36314_0
...
DEBUG 4:       plane min: 0.364983
DEBUG 4:       plane max: 0.814893

• Recommend testing for the reviewer(s) to perform, including the location of input datasets, and any additional instructions:
  
  The code for this PR is compiled on kiowa in:
  /d1/projects/MET/MET_pull_requests/met-10.0.0_beta5/feature_1753
  Please review the code changes and do whatever additional testing you'd like. Please run at verbosity 3 and 4 and notice that at level 4, the C++ code prints the python system command being executed.

• Do these changes include sufficient documentation updates, ensuring that no errors or warnings exist in the build of the documentation? [Yes]
  None needed for this change, although we should update the docs for the change pickle to NetCDF temp files.

• Do these changes include sufficient testing updates? [Yes]
  No additional testing needed.

• Will this PR result in changes to the test suite? [No]
  
  If yes, describe the new output and/or changes to the existing output:
  

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[j-opatz]

The results from a use case run were successful with the new code updates, producing the expected output that was present before the pickle switch (i.e beta3 output).