Semantic of red entries not clear

[baderas]

When I open a .bib file with Jabref and an entry has not all "required fields" ("Benötigte Felder") filled, it is marked red. This behaviour is not obvious for a new user, it should be shown a message when the mouse cursor is over the entry (or something similar) that tells the user what is wrong or missing.
It is also unintuitive that Editor and Date are listed under "required fields" but the entry is not marked red when they are missing/empty.

[oscargus]

Tooltip is a really good idea!

It is required that either editor or author is set and date or year. Not sure how this can be made more clear.

[oscargus]

There is code for tooltips stating this. However, it doesn't seem like it is working, at least on Windows 10. I also tried another approach and that did not work either...

[oscargus]

The tooltips does not seem to work in the main table at all. I open a separate issue for this in #160.

[chriba]

The tooltip does work now and states: The entry is inclomplete.