read csv header, returns prop_indices dictionary, {'label' : index}
	where label is the csv column label, and index the column index

def read_header(headerlabels, options):
    """
	read csv header, returns prop_indices dictionary, {'label' : index}
	where label is the csv column label, and index the column index
	"""

    # set input variables
    status_field = options.status_field

    # confirm that status_field exists
    status_field_matcher = re.compile(status_field)
    if not any(x for x in headerlabels if status_field_matcher.match(x)):
        print("\n The status_field column '{s}' doesn't exist\n".format(s=status_field))
        sys.exit(1)

    # initiate prop_column dictionary and csv column index
    prop_indices = {}
    index = 0

    for label in headerlabels:
        prop_indices[label] = index
        index += 1

    return prop_indices