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/element/QtStatusBar.cpp

@@ -41,7 +41,8 @@ QtStatusBar::QtStatusBar()
 	m_errorButton.setStyleSheet("QPushButton { color: #D00000; margin-right: 0; spacing: none; }");
 	m_errorButton.setIcon(utility::colorizePixmap(
 		QPixmap((ResourcePaths::getGuiPath().str() + "statusbar_view/dot.png").c_str()),
-		"#D00000"
+//		"#D00000"
+		QColor(0xD0, 0, 0)
 	).scaledToHeight(12));
 	addPermanentWidget(&m_errorButton);