ui: color schemes

Put all colors into single xml file. Accessing colors is handled via the singleton class ColorScheme. The default scheme
"bright.xml" holds the original colors. The scheme "dark.xml" is a start, but still a poor alternative. Color schemes
can be switched via the View menu.

src/lib/settings/ColorScheme.h

@@ -0,0 +1,31 @@
+#ifndef COLOR_SCHEME_H
+#define COLOR_SCHEME_H
+
+#include "data/graph/Node.h"
+#include "data/graph/Edge.h"
+#include "data/query/QueryNode.h"
+#include "settings/Settings.h"
+
+class ColorScheme
+	: public Settings
+{
+public:
+	static std::shared_ptr<ColorScheme> getInstance();
+	virtual ~ColorScheme();
+
+	std::string getColor(const std::string& key) const;
+
+	std::string getNodeTypeColor(Node::NodeType type, const std::string& state = "normal") const;
+	std::string getEdgeTypeColor(Edge::EdgeType type, const std::string& state = "normal") const;
+	std::string getQueryNodeTypeColor(QueryNode::QueryNodeType type, const std::string& state = "normal") const;
+	std::string getSyntaxColor(const std::string& key) const;
+
+protected:
+	ColorScheme();
+	ColorScheme(const ColorScheme&);
+	void operator=(const ColorScheme&);
+
+	static std::shared_ptr<ColorScheme> s_instance;
+};
+
+#endif // COLOR_SCHEME_H