Material: include some more required header files

as otherwise the parser of the clang code model raises a lot of error messages

src/Mod/Material/Gui/Array3D.h

@@ -25,6 +25,7 @@
 #include <QDialog>
 #include <QStandardItem>
 #include <QTableView>
+#include <Mod/Material/App/Materials.h>
 
 namespace MatGui
 {