Distinguish between `emission value` and `emission rate`

[l-emele]

Description of the issue

The current definition of emission value is currently somehow a mixture of a process attribute and a quantity value.

Ideas of solution

Split into two classes:

• emission value: An emission value is a ~process attribute~ quantity value that quantifies ~the output of an emission process~ an emission rate. It can be calculated using ~the~ an emission factor.
• emission rate: An emission ~value~ rate is a process attribute that ~quantifies~ describes the output of an emission process. ~It can be calculated using the emission factor of that emission process~.

I would prefer keeping the class ID OEO:00140081 for emission value as this would have the existing label.

Workflow checklist

• [ ] I discussed the issue with someone else than me before working on a solution
• [ ] I already read the latest version of the workflow for this repository
• [ ] The goal of this ontology is clear to me

I am aware that

• [ ] every entry in the ontology should have a definition
• [ ] classes should arise from concepts rather than from words