* feature_faster_unit_method > main: added constants
* feature_faster_unit_method > main: extended `file` class to dynamically save unit information
* feature_faster_unit_method > main: refactored `get_property_unit` method
1. split out case that returns the wrong type (dictionary of units) into its own method
2. cleaned up (but preserved) logic
3. refactored common part of all cases (the method which prioritises unit then value-entity then measure_class)
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Co-authored-by: raj-open <raj-open@users.noreply.github.com>
Co-authored-by: Dion Moult <dion@thinkmoult.com>
Raj