Use tags editor for auto completion preferences

[LoayGhreeb]

Closes #10952
Use tags editor for auto-completion preferences with suggestions for all standard BibTeX and BibLaTeX fields.

• Should users be able to add a field that is not a standard Bib(La)TeX field, i.e., a field not suggested?

• Why is it important to always add crossref, related, and entryset fields?

  jabref/src/main/java/org/jabref/migrations/PreferencesMigrations.java

  Lines 297 to 304 in 79ba1f0

  	private static void addCrossRefRelatedFieldsForAutoComplete(JabRefPreferences prefs) {
  	// LinkedHashSet because we want to retain the order and add new fields to the end
  	Set<String> keys = new LinkedHashSet<>(prefs.getStringList(JabRefPreferences.AUTOCOMPLETER_COMPLETE_FIELDS));
  	keys.add("crossref");
  	keys.add("related");
  	keys.add("entryset");
  	prefs.putStringList(JabRefPreferences.AUTOCOMPLETER_COMPLETE_FIELDS, new ArrayList<>(keys));
  	}

• Change in CHANGELOG.md described in a way that is understandable for the average user (if applicable)

• Tests created for changes (if applicable)

• Manually tested changed features in running JabRef (always required)

• Screenshots added in PR description (for UI changes)

• Checked developer's documentation: Is the information available and up to date? If not, I outlined it in this pull request.

• Checked documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request to the documentation repository.

[Siedlerchr]

Better use getAllFieldsWithOutInternal

1. it contains more than bibtex and biblatex fields (the additional fields for other entry types, e.g. Software or IEE)
2. they are already sorted

[LoayGhreeb]

Done

[Siedlerchr]

Why is it important to always add crossref, related, and entryset fields?

These are standard biblatex fields that are explicitly designed for linking entries together:

related field (separated values)
Citation keys of other entries which have a relationship to this entry. The relationship
is specified by the relatedtype field. Please refer to § 3.5 for further details.

I recommend reading through the biblatex manual (Section 2.1 and 2.2)
http://mirrors.ctan.org/macros/latex/contrib/biblatex/doc/biblatex.pdf

[calixtus]

Cool feature!