The error console should be resizable

[koppor]

The Window showing the Error Console (Window "Program output") should be resizable.

Refs #819

[oscargus]

See #819 as well in case someone gives it a go.

[koppor]

This is fixed at our javafx branch. The binary is available at https://builds.jabref.org/javafx/.

The PR tracking the javafx updates is available #2290