Ngen framework patch

[hellkite500]

To make the bmi implementation compatible with ngen framework, some adjustments were needed

Changes

• ensure initialize works with Path object
• return an actual type name from get_var_type
• adjust set value to handle singleton list value
• adjust get_var_nbytes to be consisten with dtype/itemsize
• adjust time units to be compatible with ngen framework

Testing

1. Ran three year simulation via ngen

Checklist

• [x] PR has an informative and human-readable title
• [x] Changes are limited to a single goal (no scope creep)
• [x] Code can be automatically merged (no conflicts)
• [x] Code follows project standards (link if applicable)
• [x] Passes all existing automated tests
• [x] Any change in functionality is tested
• [x] New functions are documented (with a description, list of inputs, and expected output)
• [x] Placeholder code is flagged / future todos are captured in comments
• [x] Project documentation has been updated (including the "Unreleased" section of the CHANGELOG)
• [x] Reviewers requested with the Reviewers tool :arrow_right: