Improve support for Look & Feels

[ctrueden]

The OptionsLookAndFeel lets you control the L&F for the active JVM. We need to improve it as follows:

• Persist the L&F setting.
• Create a LookAndFeelService that sets the initial L&F to match the persisted value.
• Add API to LookAndFeelService to change the L&F, including existing windows.

[imagesc-bot]

This issue has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/fiji-2-7-0-released/71652/20

[tferr]

This is awesome! Just wanted to mention that from now on there setting L&F with FlatLaf should work on all the 3 supported OSes. With 2.4 there was an issue in which setting FlatLaf on MacOs would break AWT dialogs, but that is now fixed, and FlatLaf makes Fiji look great on MacOS too. Details: JFormDesigner/FlatLaf#583

So to answer your question:

I also would like to make FlatLaf the default L&F, unless anyone has a reason this might cause problems?

With 2.5 there should be no problems at all. I agree it should be default.