Add basic conversion from integral types to byte array

[Michael1993]

Proposed commit message:

Adds number to byte array converter (#734 / #742)

Adds a new extension that converts numbers to their byte array
representation.

Closes: #734
PR: #742

---

PR checklist

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It is based on our contributors guidelines, especially the "writing code" section.
It shall help to check for completion of the listed points.
If a point does not apply to the given PR's changes, the corresponding entry can be simply marked as done.

Documentation (general)

• There is documentation (Javadoc and site documentation; added or updated)
• Site documentation has its own .adoc file in the docs folder, e.g. docs/report-entries.adoc
• Site documentation in .adoc file references demo in src/demo/java instead of containing code blocks as text
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Documentation (new extension)

• The docs/docs-nav.yml navigation has an entry for the new extension
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• Code adheres to code style, naming conventions etc.
• Successful tests cover all changes
• There are checks which validate correct / false usage / configuration of a functionality and there are tests to verify those checks
• Tests use AssertJ or our own PioneerAssert (which are based on AssertJ)

Contributing

• A prepared commit message exists

[scordio]

LGTM and thanks again, @Michael1993!

[nipafx]

Looks good to me.

[scordio]

Hi @Michael1993, sorry, I'm a little late to provide feedback. I have only one cosmetic point for the user guide.

[scordio]

What about argument converter instead of extension?

I'm wondering about the terminology clash with Extension.

Applies also to other sentences in this file.

[scordio]

Superseded by #751.