ui: Added history of last active symbols to UI and menu (issue 151)

* holding down back or forward button shows list of current back-forward stack
* added narrow button between back and forward to show the list
* added History menu
* moved back and forward actions to History menu
* show chronological list of recently active symbols in History menu

bug id = 151

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

@@ -11,7 +11,8 @@ class MessageSearch
 {
 public:
 	MessageSearch(const std::vector<SearchMatch>& matches)
-		: m_matches(matches)
+		: isFromSearch(true)
+		, m_matches(matches)
 	{
 	}
 
@@ -70,6 +71,8 @@ public:
 		os << getMatchesAsString();
 	}
 
+	bool isFromSearch;
+
 private:
 	const std::vector<SearchMatch> m_matches;
 };

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

@@ -0,0 +1,24 @@
+#ifndef MESSAGE_TO_UNDO_REDO_POSITION_H
+#define MESSAGE_TO_UNDO_REDO_POSITION_H
+
+#include "utility/messaging/Message.h"
+#include "utility/types.h"
+
+class MessageToUndoRedoPosition
+	: public Message<MessageToUndoRedoPosition>
+{
+public:
+	MessageToUndoRedoPosition(size_t index)
+		: index(index)
+	{
+	}
+
+	static const std::string getStaticType()
+	{
+		return "MessageToUndoRedoPosition";
+	}
+
+	size_t index;
+};
+
+#endif // MESSAGE_TO_UNDO_REDO_POSITION_H