[WIP] Use x11 selection

[koppor]

Fixes #2389.

• Distinguish between middle click and Ctrl + V.

Current solution

When SELECTION, the "selection buffer" of X11 is available, use it also at copy and paste. This is a quick solution. I cannot test it locally. I only checked that the copy and paste on windows still works.

• Change in CHANGELOG.md described
• Tests created for changes
• [n/a] Screenshots added (for bigger UI changes)
• [n/a] Manually tested changed features in running JabRef
• Check documentation status (Issue created for outdated help page at help.jabref.org?)
• [n/a] If you changed the localization: Did you run gradle localizationUpdate?

[koppor]

Hint by @mkarg (Thank you!)

One has to use https://docs.oracle.com/javase/8/javafx/api/javafx/scene/input/Clipboard.html. Otherwise, it would not work.

[snisnisniksonah]

I looked into it and found this https://bugs.openjdk.java.net/browse/JDK-8088117 and while i couldn't find anything similar for the oracle jdk i couldn't get it to work with that either.
So maybe put this on hold for now?

Using JavaFX-8 with Java8u45 on SUSE11, there is no possibility to copy/paste using mouse selection or using a click on the scroll.
See details here: http://stackoverflow.com/questions/30032290/javafx-mouse-clipboard-does-not-work-in-unix

Lowering the priority to P4. I note that this is more of an unimplemented feature than a bug (it has never been supported in FX). We will look at it for JDK 9.
Workaround: use copy/paste (CTRL-C / CTRL-V)

[koppor]

We migrate to JavaFX, so this hack is (i) not working and (ii) there is no work-around. We have to re-investigate as soon as JavaFX can cope with the secondary buffer.