ui: Added shortcuts for navigating to next and previous reference in code view

* Added new class QtCodeNavigator between QtCodeView and QtCodeFileList that handles active ids and navigation
* Pass all files as initially collapsed to code view and decide in QtCodeNavigator which ones show content
* Rewrote requesting of active snippet display to top down approach
* Display other locations focused when active location changes
* Show corresponding edges when navigating references

src/lib/utility/messaging/type/MessageCodeReference.h

@@ -0,0 +1,41 @@
+#ifndef MESSAGE_CODE_REFERENCE_H
+#define MESSAGE_CODE_REFERENCE_H
+
+#include "utility/messaging/Message.h"
+
+class MessageCodeReference
+	: public Message<MessageCodeReference>
+{
+public:
+	enum ReferenceType
+	{
+		REFERENCE_PREVIOUS,
+		REFERENCE_NEXT
+	};
+
+	MessageCodeReference(ReferenceType type)
+		: type(type)
+	{
+	}
+
+	static const std::string getStaticType()
+	{
+		return "MessageCodeReference";
+	}
+
+	virtual void print(std::ostream& os) const
+	{
+		if (type == REFERENCE_PREVIOUS)
+		{
+			os << "previous";
+		}
+		else
+		{
+			os << "next";
+		}
+	}
+
+	const ReferenceType type;
+};
+
+#endif // MESSAGE_CODE_REFERENCE_H

src/lib/utility/messaging/type/MessageRedo.h

@@ -2,9 +2,9 @@
 #define MESSAGE_REDO_H
 
 #include "utility/messaging/Message.h"
-#include "utility/types.h"
 
-class MessageRedo: public Message<MessageRedo>
+class MessageRedo
+	: public Message<MessageRedo>
 {
 public:
 	MessageRedo()

src/lib/utility/messaging/type/MessageShowReference.h

@@ -0,0 +1,33 @@
+#ifndef MESSAGE_SHOW_REFERENCE_H
+#define MESSAGE_SHOW_REFERENCE_H
+
+#include "utility/messaging/Message.h"
+#include "utility/types.h"
+
+class MessageShowReference
+	: public Message<MessageShowReference>
+{
+public:
+	MessageShowReference(size_t refIndex, Id tokenId, Id locationId)
+		: refIndex(refIndex)
+		, tokenId(tokenId)
+		, locationId(locationId)
+	{
+	}
+
+	static const std::string getStaticType()
+	{
+		return "MessageShowReference";
+	}
+
+	virtual void print(std::ostream& os) const
+	{
+		os << "index: " << refIndex << " token: " << tokenId << " location: " << locationId;
+	}
+
+	const size_t refIndex;
+	const Id tokenId;
+	const Id locationId;
+};
+
+#endif // MESSAGE_SHOW_REFERENCE_H

src/lib/utility/messaging/type/MessageUndo.h

@@ -2,9 +2,9 @@
 #define MESSAGE_UNDO_H
 
 #include "utility/messaging/Message.h"
-#include "utility/types.h"
 
-class MessageUndo: public Message<MessageUndo>
+class MessageUndo
+	: public Message<MessageUndo>
 {
 public:
 	MessageUndo()