Add summary at the end of downloads

[loehden]

Since it happens sometimes that some videos/courses are not available at a certain time, a summary at the end of downloads would be helpful. This could list the number of courses (when downloading learing paths), the number of videos downloaded, the ones missing, and the ones that already were present.

[knowbee]

This is a great suggestion. Thank you! Any assistance with this would be highly appreciated since I am very busy with work.