Add several heat generation units and heat plants

[f-innatech]

Description of the issue

Some Heating units/plants are missing at the moment. Following units/plants can be added:

• Biomass heat unit
• gas heat unit
• Hydrogen heat unit
• Oil heat unit

Related issue: Issue#1772

Ideas of solution

A x heat unit is a heat generating unit that has a boiler and uses y as a fuel input.

Axioms: has energy input some y (fuel) has part some boiler participates in some combustion thermal energy transformation

Heat Plants A x heat plant is a heat plant that has x units as parts.

Axioms: participates in some combustion thermal energy transformation has some parts x unit

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