This converts many of the animation durations to Kirigami units so that
they can be controlled system wide. It also speeds up several of the
animation durations (ex. in folio) from 800ms to 400ms to improve the
feel and responsiveness of the shell.
Move from a C++ library + QML plugin to a QML plugin only for simplicity, since the homescreen switching architecture will be done from Plasma, and so use of the shell library only needs to be from QML.
