Customizable columns

[jarruda]

• Ability to alter column order.
• Ability to remove default columns.
• Ability to add columns that reference context data.

It would be ideal if column order could be changed via drag and drop through a native egui-table feature. Consider making an issue in that project and contributing there.

[jarruda]

Add/remove columns added in e28c7e9. Still need a UI for changing column order.