* Accept conversion of fractional values
- e.g. "1/10" is a valid input value
- pint dimensions returns strange results sometimes
* Add option (default) to return value without units
- Handles conversion for "stringish" input values
* Update unit tests
* Fix return from convert_physical_value method
* Update unit tests
* Improved checking for conversion code
* Call to_base_units first
* Conversion depends on whether units are supplied or not
* Updates to unit testing
* Handle conversion of units for supplier parts
- Includes some refactoring
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