Filter filetypes to backup

[Shinra99]

The idea is to add a --filter parameter that allows you to choose whether a Filetype is going to be backuped or ignored.

So that you can download only Documents type, Images type, Video Type or a combination of those but ignore the rest.

The program detects the filetypes as long as I have seen in the debug logs. Is that really possible nowadays ? (I have started using it very recently and perhaps have missed it)

Thanks for your job, really useful and necessary.