Load QML modules in a central place + dummy QML slideshow.

src/CMakeLists.txt

src/branding/default/show.qml

src/calamares/CalamaresApplication.cpp

src/calamares/CalamaresApplication.h

src/libcalamares/utils/CalamaresUtils.cpp

src/libcalamares/utils/CalamaresUtils.h

src/libcalamaresui/CMakeLists.txt

src/libcalamaresui/InstallationViewStep.cpp

src/libcalamaresui/InstallationViewStep.h

src/libcalamaresui/slideshow/CMakeLists.txt

src/qml/CMakeLists.txt

src/qml/calamares/CMakeLists.txt

src/qml/calamares/slideshow/Presentation.qml

src/qml/calamares/slideshow/Slide.qml

src/qml/calamares/slideshow/qmldir