Button Class & MIT License Added.

XtreemNodes.cbp

@@ -41,9 +41,11 @@
 			<Add option="-lopengl32" />
 			<Add option="-lsfml-window" />
 		</Linker>
+		<Unit filename="GUI.cpp" />
 		<Unit filename="MapBlock.cpp" />
 		<Unit filename="include/Base.h" />
 		<Unit filename="include/FastNoiseLite.h" />
+		<Unit filename="include/GUI.h" />
 		<Unit filename="include/Logger.h" />
 		<Unit filename="include/MapBlock.h" />
 		<Unit filename="include/NodeRenderer.h" />