Properly handle x-kde-force-image-copy hint: https://phabricator.kde.org/D19852
Properly synchronize clipboard content and history
(deleting last item in history didn't clear the clipboard).
Keep last image in history even if we are ignoring images, but without preview
(so that we can still clear history, and the tooltip says truth about clipboard content).
Fixed tray icon tooltip text.
BUG: 409366
{F7168503}