Export single corporate author to ms office xml

[Siedlerchr]

If the author in JabRef is enclosed in curly braces .e.g {JabRef Developers} it is now recognized as corporate author and exported in the corresponding field.
This should also work for editor and other ms office author fields

Refs #1497

• Change in CHANGELOG.md described
• Tests created for changes
  - [ ] Screenshots added (for bigger UI changes)
• Manually tested changed features in running JabRef
• Check documentation status (Issue created for outdated help page at help.jabref.org?)
  - [] If you changed the localization: Did you run gradle localizationUpdate?

[tobiasdiez]

The code changes look good to me. However, probably it would be good to embed a similar logic in the AuthorList class. By the way, I have no idea why there is a class msbib.PersonName - this looks like a duplicate of Author and should probably replaced by it. Similar the parsing https://github.com/JabRef/jabref/pull/2688/files#diff-22fc42ead754a2997ddf3a14c54fdca5R112 is already handled by AuthorList.parse.

[Siedlerchr]

@tobiasdiez I now used the Author/Authorlist parsing classes. I created a new class for MsBib which is essentially a wrapper class around the Author class, but handles a few more things only relevant to MS bib.
Checking for corporate authors is not possible inside the Author parser as there are surrounding braces already stripped on calling.

[tobiasdiez]

Good job! Code looks ok now and only fetcher tests fail -> merge.