WIP: Display versions of installed packages

As @mray-guest mentioned yesterday in IRC, it would be nice to know which package versions are installed, e.g. to know whether ones box is affected by known vulnerabilities.

This MR adds a small info-sign on top right of all /sys/ and /apps/ pages that have packages installed. When hovering, a tooltip with the package versions is shown:

The downside is one additional action call for each /sys/ and /apps/ page, which is quite fast though (I didn't perceive a performance difference in my VM). If it turns out to have performance impacts the installed package versions could be cached.