F4 opens selected file in current JTable context

[stefan-kolb]

Resolves #2355

[lenhard]

I just tested this locally and it works if I have selected another file in the entry editor.

However, the following seems a little counter-intuitive to me:

1. I have the second file of an entry selected in the entry editor, everything works as expected.
2. Next, I click the same entry in the main table. Both the entry in the main table and the second file in the entry editor are still highlighted.
3. When I push F4 now, the first attached file is opened and not the one that is still highlighted in the entry editor. This seems counter-intuitive.

This is just a minor thing, and if in doubt the PR can be merged as is (code-wise it is fine). However, it would be nice if the feature were more consistent.

[stefan-kolb]

I understand this, but this is a focus problem then. I'm not sure how to fix this. Initially, I also didn't want to implement this feature here, but Olly wanted JabRef to behave like this. For me F4 opening the first link regardless of the current focus was ok.

[lenhard]

@stefan-kolb Sure, I understand. This is no blocker and from my point of view, the PR can also be merged as is. I just guess that at some point a user will stumble upon this and report it as an issue.