reorganise some settings acording changes on android & ios

[Simon-Laux]

closes #3809

[r10s]

thanks a lot for adapting the dialogs! did not look at the code, some feedback from testing:

• the button "Send Autocrypt Setup Messages" shall have same style as the other buttons (should look like "Import", "Export", "Password and Account" etc.)

• the hint "Autocrypt is a new and open specification ..." shall be removed without a replacement

• there is some space missing between "Videochat" title and value:
  
  (might be an older issue, no blocker therefore)

otherwise lgtm (i assume the missing strings will be pulled in anyways)

[Simon-Laux]

there is some space missing between "Videochat" title and value:

I'd say that could deserve its own issue, even with space it looks not good enough, maybe it could show the current instance in a subtitle? but that's a topic on it's own, if important enough then make an issue.