Refactor fields sub-delimiter and cardinality handling

[joecorall]

Link to Github issue or other discussion

#755

What does this PR do?

Simplifies the field definition implementations.

What changes were made?

• The fields definitions were checking if a sub-delimiter existed in the CSV cell and calling two separate pieces of logic in the case of existing or not existing. That can be simplified by always splitting on the sub-delimiter and handling the values that way: df1df23
• Similarly, the cardinality handling of limited vs unlimited can be simplified by handling unlimited and limited in the same if conditional: cca4d94

if -1 < cardinality < len(subvalues)
    // remove additional values over cardinality

How to test / verify this PR?

Unit tests should cover this as no new code was added, only removing if/else conditons on whether the sub-delimiter exists.

Interested Parties

@mjordan

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Checklist

• Before opening this PR, have you opened an issue explaining what you want to to do?
• Have you included some configuration and/or CSV files useful for testing this PR?
• Have you written unit or integration tests if applicable?
• Does the code added in this PR require a version of Python that is higher than the current minimum version?
• If the changes in this PR require an additional Python library, have you included it in setup.py?
• If the changes in this PR add a new configuration option, have you provided a default for when the option is not present in the .yml file?

[mjordan]

Thanks @joecorall!