QML the fallback auth dialog

CMakeLists.txt

resources/qml/Root.qml

resources/qml/dialogs/FallbackAuthDialog.qml

src/FallbackAuth.cpp

src/FallbackAuth.h

src/dialogs/FallbackAuth.cpp

src/dialogs/FallbackAuth.h

src/ui/UIA.cpp

src/ui/UIA.h