This PR will refresh the software update page so that self-hosters can more easily understand the plugins they have installed and which plugins need updates, and so that they are able to quickly and easily update them (or update everything).
Co-authored-by: Martin Brennan <mjrbrennan@gmail.com>
In this PR, all references in the UI to the word "`upgrade`" are changed to "`update`". This is to differentiate the update process in self-hosted sites from the plan "upgrade" process in hosted sites.