Performance issues

The GUI is very slow on certain operations and takes up a lot of resources. Furthermore, when started on VMware Fusion, running on macOS, it quickly takes up a lot of resources and crashes when menu items in the top menu are hovered over (see image below).


Currently, it also slows down noticeably when in the `Backend options` dialog.

Possible culprits:
- **Data bindings**: To ensure a responsive experience, in terms of feedback, a lot of the UI elements are using data bindings, which trigger a lot of internal variable updates when the user interacts with the UI. However, based on a presentation by [Sun Microsystems Inc. as JVM Lang Sumit](http://wiki.jvmlangsummit.com/images/e/ee/Field_JFX_Bind.pdf), the binding structure should have high performance.
- **Listeners**: In contrast to data bindings, listeners can trigger arbitrary functions, which means that there might be some expensive operations that are triggered on frequent and/or repeated changes of UI elements.