Add global shortcuts for switching to the previous/next activity
Summary:
We currently have a mouse-wheel action to switch to the previous/next activity,
but it wasn't possible to assign a global keyboard shortcut to these actions.
As discussed on Phabricator, this doesn't define a default key-sequence yet,
but at least gives users the possibility to assign there own ones, which wasn't
possible before.
Reviewers: apol, davidedmundson, VDG, Plasma, ngraham
Reviewed By: davidedmundson, VDG, Plasma, ngraham
Subscribers: ngraham, romangg, ivan, plasma-devel
Tags: Plasma
Differential Revision: https://phabricator.kde.org/D22382