Core update
No border for message area (as in mockup)
Merge branch 'pr855'
Update de.ts

revised all of german translation.
fixed some original translation strings
adjusted translation messages

as discusses here: https://github.com/tux3/qTox/pull/848#discussion_r20851990
Italian translation: update
Merge branch 'pr856'
Merge branch 'pr858'
Merge branch 'pr798'
Group chat button at the bottom of contact list resized to 16x16 like other buttons
Merge branch 'pr861'
Fix some nullptr dereferences in Audio

Fixes #859
Italian translation: update
Merge branch 'pr866'
also testing my signing
warn on can't read file, fixes #860
Attempt to fix #859
Window geometry saved when window is resized Splitter position saved when splitter is moved
Fixed restoring of window geometry when "Start in tray" is unchecked
move new functions to a more logical location