New MetaData serialization

[stefan-kolb]

Ideas:

• Reuse BibTeX parser logic as far as possible
• Drop custom String parsing logic
• Make it obvious which data is related to Jabref
• One Bibentry as configuration object, e.g., saveactions -> SaveAction.java

old:

@Comment{jabref-meta: databaseType:bibtex;}

new:

@JabRef{metadata,
  databasetype = {bibtex}
}

old:

@Comment{jabref-meta: saveActions:enabled;
date[normalize_date]
pages[normalize_page_numbers]
month[normalize_month]
;}

new:

@JabRef{saveActions,
  state = {enabled},
  date = {normalize_date, action2}
  pages = {normalize_page_numbers}
  month = {normalize_month}
}

[tobiasdiez]

I really like the idea! Maybe the JabRef type might lead to problems but otherwise a very readable and understandable format!

[koppor]

Refs https://github.com/JabRef/help.jabref.org/issues/227 JabRef/user-documentation#227

[koppor]

Refined issue at JabRef#10371.