Log of what happened

**Is your feature request related to a problem? Please describe.**
When reporting bugs, it would help to know what version was installed / upgraded, when, and from which repo.
After I uninstall an app, I forget the name and cannot find it again.
I want to search all apps installed from a 3rd party repo and replace with the stock F-droid variants.
...

An audit log would help answer these questions, and more.

**Describe the solution you'd like**
A list of
* app name + app version + date of installation
* app name + app version + date of **un**installation (app removal)
* repo enabled / repo disabled

**Additional context**
The log can only contain info from Droid-ify (obviously) but it's not a problem if one is not using other clients.