Improve error infos on upload failure

As reported by @Bugsbane

> Oh, something else that I was also running into, but I'm assuming is my Nginx setup - not the Android app - is that files over 1gb seem to fail when uploading. Even so, if possible it would be nice to let the user know why uploads failed.
>
> Uploads view: Just the filename and then "Upload failed"

I think we should improve in this area, either via displaying a more detailed message or via activating the logging on stable clients (see #247) to give people the change to gain some more information. In general though I think more detailed error message might confuse since non-tech users might get confused but for error reporting and knowing what is going on it might be critical information.
With failed downloads might might anyways have to implement some auto-restart, e.g. on the next wifi connect or else so users wouldn't even have to look into the uploads view and investigate...

what do you think @tobiasKaminsky and also @nextcloud/designers also from the UX/UI perspective since infos might get very technical