Change icon_name to type

icon_name is the wrong variable name here. The GUI does not only change the icon name based on the type. There will be several other properties that change with the type. The more general name type fits better here.

Author: zsoerenm

src/systems/abstractsystem.jl

@@ -1,7 +1,7 @@
 const SYSTEM_COUNT = Threads.Atomic{UInt}(0)
 
 struct GUIMetadata
-    icon_name::String
+    type::String
     layout::Any
 end