Add automated label creation/suggestion for oeo-composer tool for units

[stap-m]

Description of the issue

In #1712 and #1679 the oeo-composer tool is created. The first step is to make it available for units. Here's the pattern from the publication of oeox

To ensure meaningful labels for the uncurated oeox, an automated label generator should suggest a label. I propose the following pattern for the labelling:

Ideas of solution

1. For all NUMERATORS, i.e. units that are related to the created class via has linear unit numerator or has squared unit numerator or has cubed unit numerator, process in order of appearance:
   1.1 Is the used relation "squared" or "cubic"? If yes, add "squared" or "cubic" resp.
   1.2 Is there unit related to a prefix? If yes, add prefix, e.g. Mega.
   1.3 Add unit
   1.4 Is there another NUMERATOR? If yes, add the term "and" and continue with 1.1. If not, so 2.
2. Are there unit related as denominators? If yes, add the term "per" and proceed with 3. Else, label is finished.
3. For all DENOMINATOR, i.e. units that are related to the created class via has linear unit denominator or has squared unit denominator or has cubed unit denominator, process in order of appearance:
   3.1 Is the used relation "squared" or "cubic"? If yes, add "squared" or "cubic" resp.
   3.2 Is there unit related to a prefix? If yes, add prefix, e.g. Mega.
   3.3 Add unit
   3.4 Is there another DENOMINATOR? If yes, add the term "and" and continue with 3.1. Else, label is finished.

I suppose there won't be units that have no numerator. We could either suggest the created label and allow the user to change it, or keep the generated label as main label and allow the users to add a secondary label "iao:alternative label" that is kind of a synonym.

FYI @l-emele @nelekoehler

Workflow checklist

• I am aware of the workflow in CONTRIBUTING.md