Misc fixes

- changed HEADER_SIZE constant from 8 to 7 to reflect message structure
- removed duplicate utility folder in UIPEthernet that prevented proper
compilation
- removed unnecessary includes in EthernetGateway that prevented proper
compilation

libraries/UIPEthernet/utility/uip_debug.h

@@ -1,18 +0,0 @@
-#ifndef UIP_DEBUG_H
-#define UIP_DEBUG_H
-extern "C" {
-  #import "utility/uip.h"
-}
-
-class UIPDebug {
-
-public:
-
-  static void uip_debug_printconns();
-  static bool uip_debug_printcon(struct uip_conn *lhs,struct uip_conn *rhs);
-  static void uip_debug_printbytes(const uint8_t *data, uint8_t len);
-
-};
-
-
-#endif