Add a ported example configuration for the Velleman K8400 (Vertex) printer.

Supports both dual and single head printers (with the correct config).
Includes community sourced feed rate fix.

Rename / move files.

Remove redundant definitions.

Marlin/pins.h

@@ -77,6 +77,8 @@
   #include "pins_3DRAG.h"
 #elif MB(K8200)
   #include "pins_K8200.h"
+#elif MB(K8400)
+  #include "pins_K8400.h"
 #elif MB(TEENSYLU)
   #include "pins_TEENSYLU.h"
 #elif MB(RUMBA)