[RFE] Improve Headless UX for desktop app

[illume]

Current situation

"Headless mode" is when the Headlamp app uses the browser window rather than an Electron app window.

Currently

• the headless app opens a browser window/tab, and then when someone closes that tab the server is still running.
• the default behaviour is to not use headless mode.

Impact

When the browser tab is closed the backend server keeps running.

Ideal future situation

There's no way to:

• close a headless app from within the browser.
• open a browser tab for the app when a browser tab is closed.

Implementation options

• Have a on close window handler when asks the user "Do you want to close app?", or simply closes the backend server.
• For changing the default to headless mode, have a build time configuration to make that the default.