This makes it possible to remove QML from Calamares, possibly yielding
a smaller, lighter installer; it takes with it the nice slideshow,
modern configurable navigation and the QML UIs built for various modules.
By default, WITH_QML is on and the "normal" feature set is retained.
- look for Qml modules only when WITH_QML is on (the default)
- look for Network, since that's pulled in only implicitly
- disable the QML Calamares models (modules/*q) if no QML is
enabled; longer-term plan is to merge the **pages** back to
the "upstream" modules, and have things be run-time switchable,
but that's not here yet. Also disable the notesqml module when
QML is off.
- Don't need an extra indirection from WITH_KF5Crash to WITH_KCRASH,
just use the cmakedefine directly.
- Since the setting is only used in main.cpp, move the define
down there and remove cmakedefine entirely.
Honor SYSCONFDIR as specified by CMake arguments instead of
using a hard-coded path.
Since GNUInstallDirs set CMAKE_INSTALL_FULL_SYSCONFDIR to
CMAKE_INSTALL_PREFIX/etc we need to change the default ourselves.
