Align layershell-qt with the rest of KDE frameworks at a licence level
Makes it possible to use in certain places that otherwise it couldn't be.
Signed-off-by: Victoria Fischer victoria.fischer@mbition.io
Relicenced according to https://community.kde.org/Policies/Licensing_Policy
CC @davidre @davidedmundson @vladz @nicolasfella @mart @vkrause