Clarify button "Import and keep old entry"

[koppor]

Refs #6190

The button text "Import and keep old entry" does not make it crystal clear, what happens.

My use case:

1. Copy 120 entries (which are no duplicates) from a bib file
2. Paste these entries in a new file
3. The merge entries dialog pops up
4. I want to keep both entries (and not creating a new one)

[koppor]

Maybe, the call of the dialog is wrong. Sometimes, it is "Use both entries"

[Siedlerchr]

Comes from pasting:
importHandler#importEntryWithDuplicateCheck -> calls the dialog with IMPORT_CHECK enum value which is not covered in the existing cases in the DuplicateResolverDialog

[HoussemNasri]

There are 7 possible actions/strategies, one might choose to fast-merge entries, but in the duplicate resolver dialog, only 4 are provided ('Cancel' and 'Do not import entry' seems to do the same thing)

• Keep Left
• Keep Right
• Keep Merged
• Keep Left & Right
• Keep Left & Merged
• Keep Right & Merged
• Keep Left & Right & Merged

I don't think we can fit 7 actions on the button bar. Even if we did it will look ugly. I believe that using Controlsfx's CheckComboBox would be a better solution. We add left, right and merged to the ComboBox and users can select whatever combination they like. We can also change left and right to Old entry and from Import if entries are imported.

[koppor]

I am in favor of:

• Keep Merged (at the beginning, because this should be the best)
• Keep Left
• Keep Right
• Keep Left & Right (this is only necessary, because our duplicate detection is not that good)