prop(unicorn): Replace logout button with system menu

[ajstrongdev]

https://github.com/rhino-linux/tracker/issues/15

ajstrongdev created this issue in rhino-linux/tracker

open prop(unicorn): Replace logout button with system menu #15

Replace the logout button on the left hand side of the panel with a system menu similar to that found on macOS. I have quickly mocked up an example utilising a custom menu found here: https://www.xfce-look.org/p/1529470  - Changes will be required to make it fit for Rhino Linux, and i do believe a custom icon would be better for the icon as opposed to the standard Rhino Linux icon.