Show plugin installation progress in new UI
While a plugin is being installed, only a spinner is shown. There is no way for the user to tell how long it will take or if the system is actually doing anything.
This should be a status display for the download and install of the plugin jail. If we already have that for jails, the code can be reused.
The attached screenshot was taken after about two minutes in the plugin install. It finally finished installing after about 4.5 minutes.