Add automatic validation after chart installation

[quirsh]

Hey,
I recently encountered a problem with missing charts due to a temporary storage (/run/user/1000) being too small during install causing the unzipping of the charts to be interrupted.
The installation process seemed successful, it showed even the "validating download" message and gave no error. On the first look the charts were all there but when you zoomed in on certain spots you could discover missing charts.

This is a unlucky and potentially dangerous situation, therefore I would like to suggest:
Add the existing "Validate chart set" routine to the installation process and warn the user in case the chart set was not installed completely for some reason.

Many thanks!