src: clazy compiler warnings

get rid of most clazy warnings (https://github.com/KDE/clazy)
* range loop use refs
* qcolor ctor with ints
* missing Q_OBJECT macro
* use .constfirst instead of .first

enabled ccache for unix systems for fasterr recompiling
* if ccache is in path we use it now

src/lib_gui/qt/window/QtSelectPathsDialog.h

@@ -9,6 +9,7 @@ class QListWidget;
 class QtSelectPathsDialog
 	: public QtTextEditDialog
 {
+	Q_OBJECT
 public:
 	QtSelectPathsDialog(const QString& title, const QString& description, QWidget* parent = 0);