Grey-out auto upload options until enabled

[mario]

As suggested by @gahujipo here: #797 (comment)

The preferences window for auto upload shows a switch next to "Preferences for auto uploading". At the first sight it was not clear to me that that switch is uses to enable the auto upload feature for that folder pair. My idea was to grey out the options in the window unless the switch is set to true.

[tobiasKaminsky]

Nice idea 👍
(silently assuming that you also like the idea as you have created this issue ;-) )

[mario]

Yup, like the idea. That's called good UX :P