D5605: Allow multiple categories with the same name

[Marco Martin]

mart added a reviewer: whiting.

REPOSITORY
  R304 KNewStuff

REVISION DETAIL
  https://phabricator.kde.org/D5605

To: mart, #plasma, leinir, whiting
Cc: plasma-devel, #frameworks, spstarr, progwolff, Zren, lesliezhai, 
ali-mohamed, jensreuterberg, abetts, sebas, apol, lukas