Prettify unpack_assessment_zip output

[MCGallaspy]

On develop:

With the Windows installer, we now call unpack_assessment_zip as part of the installation process. It's output is displayed on a console, but it's really minimal (Unpacking...) and can take a long time. Some users will undoubtedly think that it is hung, and inadvertently cancel it, resulting in a failed installation. So let's give it better output -- some kind of progress bar. Something that will quell the rising panic in our user's throats.

[benjaoming]

This issue lives on in #5356