ait-create-dirs documentation inconsistencies

The ait-create-dirs help text incorrectly states what example calls are doing.

usage: ait-create-dirs [-h] [-d <YYYY-MM-DDTHH:mm:ssZ>] [-t <days>]

    AIT Create Directories Script

    Based on the data paths specified in the AIT_CONFIG, this software creates
    daily directories for the GDS based on the paths and any applicable variable
    substitution.

optional arguments:
  -h, --help            show this help message and exit
  -d <YYYY-MM-DDTHH:mm:ssZ>, --date <YYYY-MM-DDTHH:mm:ssZ>
                        Create directory structure using thisISO 8610 datetime
                        for strftime replacementin directory path. Default:
                        TODAY
  -t <days>, --timedelta <days>
                        Number of days in the future you would like to create
                        a directory.Default: 0

    Create directories based on some set of variables in a separate YAML config

        $ ait-create-dirs -c vars.yaml

    Create directories starting 3 days from now for 90 days

        $ ait-create-dirs -d 2016-01-01T00:00:00Z

The -c flag example uses an argument that doesn't exist. The -d example incorrectly states that it's creating a range of directories. These need updated.

The docstring for the module needs updated to change references from oco3 to ait to avoid confusion. We should also use this docstring in the argparse documentation so it's not going to waste / out of date.

Start at the ait-create-dirs module docstring and its argparse help text. Update the examples so they match the available arguments and behavior, replace oco3 references with ait, and use the module docstring in the argparse documentation; done means the displayed help is consistent and no outdated references remain.