Allow for unit standardisation in CLI output

[amorphic]

As a CLI user I need to be able to define a standard unit for each unit type so that I can:

1. More easily read measurement results - they are currently in high-precision units that are hard for humans to grok
2. Compare results from different measurements in the same run.

This card will be complete when a CLI user can define standard units for each unit type and all results are converted to and displayed in these units.

[amorphic]

In #8 we add a standard means of converting between units of a given type. We can use that functionality here.