D8734: use OCS to retrieve Tabs from the KDE store

[Harald Sitter]

sitter added a reviewer: jriddell.

REPOSITORY
  R106 KSysguard

REVISION DETAIL
  https://phabricator.kde.org/D8734

To: sitter, #plasma, leinir, jriddell
Cc: plasma-devel, ZrenBot, progwolff, lesliezhai, ali-mohamed, jensreuterberg, 
abetts, sebas, apol, mart