GH-1559 Fix FTB icons

This was caused by separation of GUI and logic. Now logic has an interface that GUI implements.
It should be expanded upon later.

api/logic/icons/IIconList.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <QString>
+
+enum IconType : unsigned
+{
+	Builtin,
+	Transient,
+	FileBased,
+	ICONS_TOTAL,
+	ToBeDeleted
+};
+
+class IIconList
+{
+public:
+	virtual ~IIconList(){}
+	virtual bool addIcon(QString key, QString name, QString path, IconType type) = 0;
+};
+