Use only KDECompilerSettings, not also KDEFrameworkCompilerSettings
The latter is only for KF modules to use.
Also include the KDE cmake modules as first thing, as their settings can influence other included macros. And drop outdated flags QT_USE_FAST_CONCATENATION & QT_USE_FAST_OPERATOR_PLUS, superceded by QT_USE_QSTRINGBUILDER