Pull duplicated functions into a common directory

[NParsonsMO]

As mentioned in this comment:
#130 (comment)

The functions

• write_recipe in CMEW/app/configure_for/bin/update_recipe_file.py and
• write_dict_to_yaml in CMEW/app/add_datasets/bin/add_datasets_to_share.py
  are actually the same function (one with a more generic name) and should be pulled into a common directory.

CMEW/lib/python/ automatically gets added to PYTHONPATH when the workflow is run, so I initially experimented with writing write_recipe into CMEW/lib/python/common.py. The changes to unit tests (mostly the ability to run them locally) made this into a larger piece of work than anticipated, so I'm writing this as a separate issue.

[NParsonsMO]

CMEW/lib/python/ is the place we will (have to?) use in order to process the namelist sections into a python dictionary format for putting into Jinja2.